Showed Sequence Similarity Research Articles

A new isolate of mungbean yellow mosaic India virus in Vigna mungo L. reported from a Dayalbagh field, Agra.

Black gram (Vigna mungo L.) plants showing yellow mosaic symptoms during 2019-2022 crop seasons were collected randomly from a Dayalbagh field, Agra Region of Uttar Pradesh, India. Total genomic DNA was isolated from the infected leaf samples by the Cetyltrimethylammonium bromide (CTAB) method and subjected to PCR. After viral confirmation, the viral genome was amplified by rolling circle amplification following the standard protocol. The DNA A and DNA B subgenomes were cloned individually as a PstI and BamHI fragment in the pUC18 vector. Positive clones were subjected to DNA sequencing. The results revealed that DNA A and DNA B show the closest nucleotide identity with "mungbean yellow mosaic India virus-[Mungbean], DNA-A, the complete sequence" (GeneBank Accession No AF416742.1) with 98.14% identity, and "mungbean yellow mosaic India virus isolate Mu1-Dholi segment DNA-B, the complete sequence" (GeneBank Accession No MW814723.1) with 97.94% identity, respectively. The new isolate of mungbean yellow mosaic India virus (MYMIV) shows sequence similarity with the coat protein gene of various strains of MYMIV. In the new isolate of MYMIV, a point mutation wasobserved at the 2036th nucleotide of DNA B, which disrupts the reading frame to introduce a stop codon and thus leading to a decrease in the size of the movement protein gene. In the present study we are reporting the whole genome sequence of the MYMIV Dayalbagh isolate for the first time.

Metabolite phosphatase from anhydrobiotic tardigrades.

Terrestrial organisms have systems to escape from desiccation stresses. For example, tardigrades (also known as water bears) can survive severe dried and other extreme environments by anhydrobiosis. Although their extraordinary ability has enchanted people, little is known about the detailed molecular mechanisms of anhydrobiosis. Here, we focused on the tardigrade Ramazzottius varieornatus, one of the toughest animals on Earth. A transcriptome database of R. varieornatus shows that genes encoding a Ferritin-like protein are upregulated during desiccation or ultraviolet radiation. This protein shows sequence similarity to enigmatic proteins in desiccation-tolerant bacteria and plants, which are hypothesized to be desiccation-related. However, because these proteins lack detailed biological information, their functions are relatively unknown. We determined an atomic (1.05 Å) resolution crystal structure of a Ferritin-like protein from R. varieornatus. The structure revealed a dinuclear metal binding site, and we showed that this Ferritin-like protein has phosphatase activity toward several metabolite compounds including unusual nucleotide phosphates produced by oxidative or radiation damage. We also found that a homologous protein from a desiccation- and ultraviolet-tolerant bacterium Deinococcus radiodurans is a metabolite phosphatase. Our results indicate that through cleaning up damaged metabolites or regulation of metabolite levels, this phosphatase family can contribute to stress tolerances. This study provides a clue to one of the universal molecular bases of desiccation-stress tolerance.

Identification of a novel member of the genus Laulavirus (family Phenuiviridae) from the entomopathogenic ascomycete fungus Cordyceps javanica.

The virus family Phenuiviridae (order Hareavirales, comprising segmented negative-sense single stranded RNA viruses) has highly diverse members that are known to infect animals, plants, protozoans, and fungi. In this study, we identified a novel phenuivirus infecting a strain of the entomopathogenic fungus Cordyceps javanica isolated from a small brown plant hopper (Laodelphax striatellus), and this virus was tentatively named "Cordyceps javanica negative-strand RNA virus 1" (CjNRSV1). The CjNRSV1 genome consists of three negative-sense single stranded RNA segments (RNA1-3) with lengths of 7252, 2401, and 1117 nt, respectively. The 3'- and 5'-terminal regions of the RNA1, 2, and 3 segments have identical sequences, and the termini of the RNA segments are complementary to each other, reflecting a common characteristic of viruses in the order Hareavirales. RNA1 encodes a large protein (∼274 kDa) containing a conserved domain for the bunyavirus RNA-dependent RNA polymerase (RdRP) superfamily, with 57-80% identity to the RdRP encoded by phenuiviruses in the genus Laulavirus. RNA2 encodes a protein (∼79 kDa) showing sequence similarity (47-63% identity) to the movement protein (MP, a plant viral cell-to-cell movement protein)-like protein (MP-L) encoded by RNA2 of laulaviruses. RNA3 encodes a protein (∼28 kDa) with a conserved domain of the phenuivirid nucleocapsid protein superfamily. Phylogenetic analysis using the RdRPs of various phenuiviruses and other unclassified phenuiviruses showed CjNRSV1 to be grouped with established members of the genus Laulavirus. Our results suggest that CjNRSV1 is a novel fungus-infecting member of the genus Laulavirus in the family Phenuiviridae.

Unveiling unknown transcripts and exons: Insights into durian var. D24 (Durio zibethinus Murr.) fruit development and ripening

Durian (Durio zibethinus Murr.) plant fruits are popular among Southeast Asians. This study aimed to characterise the gene expression during the growth and development of durian fruit at its young, mature, and ripening stages. We used a high-throughput RNA Sequencing approach to identify and characterise unknown transcripts (UTs) from durian fruit pulp transcriptomes. The categorisation of UTs relied on assessing their coding potential and conducting sequence analysis, followed by thorough manual curation. After mapping, 110 million high-quality reads were analysed for each of the nine samples, revealing that each contains 76,700 to 89,117 distinct transcripts and 561,211 to 646,291 exons. In the present analysis, we emphasised identifying and classifying UTs, disregarding transcripts with accurate annotations. Differential expression analysis identified 280 significant unknown transcripts, presumably involved in various biological functions in durian growth. The top BLASTn comparative analysis results for 183 unknown transcripts (UTs) primarily showed significant homology, ranging from 80 % to 100 %, with transcripts from closely related species within the Malvaceae family, including Bombax ceiba, Gossypium hirsutum, Gossypium raimondii, Herrania umbratica, and Theobroma cacao. Functional annotation showed that many upregulated UTs may encode protein-coding genes involved in cellular and metabolic activities, catalytic and electron transfer activities, cellular and anatomical entities, and protein-containing complexes. Out of 97 UTs that do not have a BLASTn hit, 2 of them match GO terms, TCONS 00034019 and TCONS 00058246, corresponding to the InterPro GO Names, namely P: positive regulation of organ growth (GO:0046622) and F: calcium ion binding (GO:0005509). Three open reading frame (ORF) sequences longer than 300 nucleotides were identified as potential protein-coding genes through SMARTBLAST analysis, showing sequence similarities with Retropepsins, pepsin-like aspartate proteases, DUF4492 domain-containing protein, and a hypothetical protein CTI12_AA006750 in UniProtKB/Swiss-Prot. In conclusion, this study sheds light on the dynamic gene expression patterns during durian fruit development. It highlights the significance of characterising unknown transcripts and their potential roles in biological processes, thus enhancing our understanding of durian genetics.

Spathaspora quercus f.a., sp. nov., a novel yeast isolated from rotting wood and a lichen sample in Kyushu region, Japan.

Four novel d-xylose assimilation yeast strains were isolated from rotting wood and a lichen sample collected in the Kyushu region of Japan. Species identifications were performed by analysing the internal transcribed spacer 5.8S region sequences and the D1/D2 variable domain of the large subunit rRNA gene. Phylogenetic analysis suggested that these isolates are closely related to Spathaspora species isolated in China, such as S. jiuxiensis and S. parajiuxiensis. These isolates also showed sequence similarity to deposited sequences labelled as Schwanniomyces. They did not produce asci and ascospores under any of the test conditions. Based on phylogenetic analysis and phenotypic differences, Spathaspora quercus f.a., sp. nov. is proposed to accommodate these isolates. The holotype of Spathaspora quercus f.a., sp. nov. is NBRC 116146T (CBS18366). This species is able to ferment d-xylose, and a d-xylose fermentation test revealed that this species produces a considerable amount of xylitol.

Identification and nucleotide sequencing of a novel partitivirus derived from Rhizoctonia solani AG-4 HG III isolate A14.

Rhizoctonia solani is a widely disseminated phytopathogen that is found in the soil and is capable of harming many important species of crops. Here, analysis of the R. solani AG-4 HG III strain A14 led to the identification of a novel mycovirus assigned the tentative name "Rhizoctonia solani partitivirus A14" (RsPV-A14), which was subjected to sequencing and associated analyses. This approach revealed that RsPV-A14 harbored two dsRNA segments, 2022 bp (dsRNA1) and 1905 bp (dsRNA2) in length. dsRNA1 was found to contain a single open reading frame (ORF1) that codes for a 622-amino-acid protein with conserved RNA-dependent RNA polymerase (RdRp) motifs, and dsRNA2 was found to contain an ORF (ORF2) that is predicted to code for a 558-amino-acid capsid protein (CP). BLASTp analysis using the putative RdRp of RsPV-A14 showed sequence similarity to partitiviruses, including Rosellinia necatrix partitivirus 7 (50.53% identity), an unclassified partitivirus. Phylogenetic analysis based on RdRp protein sequences suggested that RsPV-A14 is a novel member of the family Partitiviridae.

Structural and functional characterization of the novel endo-α(1,4)-fucoidanase Mef1 from the marine bacterium Muricauda eckloniae.

Fucoidanases (EC 3.2.1.-) catalyze the hydrolysis of glycosidic bonds between fucose residues in fucoidans. Fucoidans are a compositionally and structurally diverse class of fucose-containing sulfated polysaccharides that are primarily found in brown seaweeds. Here, the structural characterization of a novel endo-α(1,4)-fucoidanase, Mef1, from the marine bacterium Muricauda eckloniae is presented, showing sequence similarity to members of glycoside hydrolase family 107. Using carbohydrate polyacrylamide gel electrophoresis and nuclear magnetic resonance analyses, it is shown that the fucoidanase Mef1 catalyzes thecleavage of α(1,4)-linkages between fucose residues sulfated on C2 in the structure [-3)-α-L-Fucp2S-(1,4)-α-L-Fucp2S-(1-]n in fucoidan from Fucus evanescens. Kinetic analysis of Mef1 activity by Fourier transform infrared spectroscopy revealed that the specific Mef1 fucoidanase activity (Uf) on F.evanescens fucoidan was 0.1 × 10-3 Uf µM-1. By crystal structure determination of Mef1 at 1.8 Å resolution, a single-domain organization comprising a (β/α)8-barrel domain was determined. The active site was in an extended, positively charged groove that is likely to be designed to accommodate the binding of the negatively charged, sulfated fucoidan substrate. The active site of Mef1 comprises the amino acids His270 and Asp187, providing acid/base and nucleophile groups, respectively, for the hydrolysis of glycosidic bonds in the fucoidan backbone. Electron densities were identified for two possible Ca2+ ions in the enzyme, one of which is partially exposed to the active-site groove, while the other is very tightly coordinated. A water wire was discovered leading from the exterior of the Mef1 enzyme into the active site, passing the tightly coordinated Ca2+ site.

Molecular characterization of multidrug resistant (MDR) clinical isolates of Pseudomonas aeruginosa from Nsukka, South Eastern Nigeria.

P. aeruginosa is an important nosocomial pathogen with increasing resistance to antibiotics. Objective: This study was performed to evaluate the genetic relatedness of MDR clinical isolates of P. aeruginosa. A total of 1000 samples were analysed in the study. Antibiotic resistance profiles of the isolates were determined using Kirby Bauer disk diffusion method. Polymerase chain reaction (PCR) and sequencing were simultaneously used to detect the consensus region of 16S rRNA. Genetic relatedness of the isolates was determined using restriction patterns from ALU 1 digest and random amplified polymorphic DNA. Out of the 192 P. aeruginosa isolates recovered, 136 (78.83%) were multidrug resistant. Sequence analysis of the confirmed isolates (80.68%) revealed that all the isolates shared homology with each other and also showed sequence similarity to known strains of P. aeruginosa (ATCC 27853; KT 315654; KU 321274 and KT894767). The PCR-Restriction fragment length polymorphism (PCR-RFLP) analysis revealed that there was a lot of genetic relatedness among the isolates. The RFLP finger printing technique detected seven distinct RFLP types among the isolates. Thus, study shows that there is high prevalence of MDRPA and high degree of genetic relatedness among the MDRPA isolates circulating in Nsukka area.

Prevalence and Genomic Characterization of Rotavirus A from Domestic Pigs in Zambia: Evidence for Possible Porcine-Human Interspecies Transmission.

Rotavirus is a major cause of diarrhea globally in animals and young children under 5 years old. Here, molecular detection and genetic characterization of porcine rotavirus in smallholder and commercial pig farms in the Lusaka Province of Zambia were conducted. Screening of 148 stool samples by RT-PCR targeting the VP6 gene revealed a prevalence of 22.9% (34/148). Further testing of VP6-positive samples with VP7-specific primers produced 12 positives, which were then Sanger-sequenced. BLASTn of the VP7 positives showed sequence similarity to porcine and human rotavirus strains with identities ranging from 87.5% to 97.1%. By next-generation sequencing, the full-length genetic constellation of the representative strains RVA/pig-wt/ZMB/LSK0137 and RVA/pig-wt/ZMB/LSK0147 were determined. Genotyping of these strains revealed a known Wa-like genetic backbone, and their genetic constellations were G4-P[6]-I5-R1-C1-M1-A8-N1-T1-E1-H1 and G9-P[13]-I5-R1-C1-M1-A8-N1-T1-E1-H1, respectively. Phylogenetic analysis revealed that these two viruses might have their ancestral origin from pigs, though some of their gene segments were related to human strains. The study shows evidence of reassortment and possible interspecies transmission between pigs and humans in Zambia. Therefore, the "One Health" surveillance approach for rotavirus A in animals and humans is recommended to inform the design of effective control measures.

Bioplastic (Polyhydroxyalkanoate) producing Indigenous Bacteria from Agricultural Soil Samples

Polyhydroxyalkanoate (PHA) is the naturally occurring biopolymer produced by the microorganisms. It is biodegradable and having physicochemical properties similar to conventional synthetic plastics and it can be used as an alternative to plastics. PHA is produced by microorganisms including bacteria, archaea and fungi. It gets accumulated inside the microorganisms as crystal in the presence of excess source of carbon, nitrogen, sulphur, oxygen and limited source of other nutrients. In this study PHA producing strain was isolated from agricultural soil sample. All the isolates obtained were screened for PHA production by using Nile red and Sudan black dyes. The potential isolate was characterized by biochemical tests and identified using 16S rRNA sequencing. The isolate showed sequence similarity with Priestia aryabhattai B8W22 and was designated as Priestia aryabhattai VITJK01. For PHA production, seed culture was prepared and inoculated in mineral salt medium containing glucose as a carbon source. PHA was extracted from cell dry weight biomass using methanolysis. It produced polyhydroxybutyrate (PHB) compounds including dodecane, penta decanoic acid, octadecanoic acid and heptadecanoic acid identified by Gas Chromatography Mass Spectrometry. Based on the results, it can be concluded that Priestia aryabhattai VITJK01 is a potential source for PHA/PHB production.

Investigation of lncRNA in Bos taurus Mammary Tissue during Dry and Lactation Periods.

This study aims to collect RNA-Seq data from Bos taurus samples representing dry and lactating mammary tissue, identify lncRNA transcripts, and analyze findings for their features and functional annotation. This allows for connections to be drawn between lncRNA and the lactation process. RNA-Seq data from 103 samples of Bos taurus mammary tissue were gathered from publicly available databases (60 dry, 43 lactating). The samples were filtered to reveal 214 dry mammary lncRNA transcripts and 517 lactating mammary lncRNA transcripts. The lncRNAs met common lncRNA characteristics such as shorter length, fewer exons, lower expression levels, and less sequence conservation when compared to the genome. Interestingly, several lncRNAs showed sequence similarity to genes associated with strong hair keratin intermediate filaments. Human breast cancer research has associated strong hair keratin filaments with mammary tissue cellular resilience. The lncRNAs were also associated with several genes/proteins that linked to pregnancy using expression correlation and gene ontology. Such findings indicate that there are crucial relationships between the lncRNAs found in mammary tissue and the development of the tissue, to meet both the animal's needs and our own production needs; these relationships should be further investigated to ensure that we continue to breed the most resilient, efficient dairy cattle.

Mechanistic study on the anti-proinflammatory activity of Kunitz type inhibitor from Caesalpinia decapetala seeds.

The study reports the biochemical characterization and mechanism of action of a novel 19.6 kDa protease inhibitor (PIs) isolated from the seeds of Caesalpinia decapetala belonging to the Fabaceae family. A systematic study was performed to ascertain the purity, specificity, biochemical and structural characterization, and its potential in curbing inflammation in vitro conditions. A two-step chromatography technique was used to purify the PIs. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization time of flightwere employed to detect the molecular mass of the protein. N-terminal sequence analysis of the inhibitor showed sequence similarity with the Kunitz family PIs. The in vitro test tube assay was performed for determining the anti-inflammatory activity and the inhibitor is antiproliferative against macrophage (RAW264.7) and lung cancer cell lines (A549). An effective decrease in the release of inflammatory mediators (NO, IL-6, TNF-α) and on the activity of elastase was observed in macrophage cell lines (RAW264.7) which were treated with PIs. The purified inhibitor shows promising results against inflammation.

Structural and functional characterisation of Tst2, a novel TRPV1 inhibitory peptide from the Australian sea anemone Telmatactis stephensoni

Sea anemone venoms are complex mixtures of biologically active compounds, including disulfide-rich peptides, some of which have found applications as research tools, and others as therapeutic leads. Our recent transcriptomic and proteomic studies of the Australian sea anemone Telmatactis stephensoni identified a transcript for a peptide designated Tst2. Tst2 is a 38-residue peptide showing sequence similarity to peptide toxins known to interact with a range of ion channels (NaV, TRPV1, KV and CaV). Recombinant Tst2 (rTst2, which contains an additional Gly at the N-terminus) was produced by periplasmic expression in Escherichia coli, enabling the production of both unlabelled and uniformly 13C,15N–labelled peptide for functional assays and structural studies. The LC-MS profile of the recombinant Tst2 showed a pure peak with molecular mass 6 Da less than that of the reduced form of the peptide, indicating the successful formation of three disulfide bonds from its six cysteine residues. The solution structure of rTst2 was determined using multidimensional NMR spectroscopy and revealed that rTst2 adopts an inhibitor cystine knot (ICK) structure. rTst2 was screened using various functional assays, including patch–clamp electrophysiological and cytotoxicity assays. rTst2 was inactive against voltage-gated sodium channels (NaV) and the human voltage-gated proton (hHv1) channel. rTst2 also did not possess cytotoxic activity when assessed against Drosophila melanogaster flies. However, the recombinant peptide at 100 nM showed >50% inhibition of the transient receptor potential subfamily V member 1 (TRPV1) and slight (∼10%) inhibition of transient receptor potential subfamily A member 1 (TRPA1). Tst2 is thus a novel ICK inhibitor of the TRPV1 channel.

Marinobacterium lacunae sp. nov. isolated from estuarine sediment.

A novel motile bacterium was isolated from a sediment sample collected in Kochi backwaters, Kerala, India. This bacterium is Gram negative, rod shaped, 1.0-1.5µm wide, and 2.0-3.0µm long. It was designated as strain AK27T. Colonies were grown on marine agar displayed circular, off-white, shiny, moist, translucent, flat, margin entire, 1-2mm in diameter. The major fatty acids identified in this strain were C18:1 ω7c, C16:0, and summed in feature 3. The composition of polar lipids in the strain AK27T included phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, one unidentified amino lipid, two unidentified aminophospholipids, two unidentified phospholipids, and six unidentified lipids. The genomic DNA of strain AK27T exhibited a G+C content of 56.4mol%. Based on the analysis of 16S rRNA gene sequence, strain AK27T showed sequence similarity to M. ramblicola D7T and M. zhoushanense WM3T as 98.99% and 98.58%, respectively. Compared to other type strains of the Marinobacterium genus, strain AK27T exhibited sequence similarities ranging from 91.7% to 96.4%. When compared to Marinobacterium zhoushanense WM3T and Marinobacterium ramblicola D7T, strain AK27T exhibited average nucleotide identity values of 80.25% and 79.97%, and dDDH values of 22.9% and 22.6%, respectively. The genome size of the strain AK27T was 4.55Mb, with 4,229 coding sequences. Based on the observed phenotypic and chemotaxonomic features, and the results of phylogenetic and phylogenomic analysis, this study proposes the classification of strain AK27T as a novel species within the genus Marinobacterium. The proposed name for this novel species is Marinobacterium lacunae sp. nov.

Identification of the glycosylphosphatidylinositol-specific phospholipase A2 (GPI-PLA2) that mediates GPI fatty acid remodeling in Trypanosoma brucei

The biosynthesis of glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) in the parasitic protozoan Trypanosoma brucei involves fatty acid remodeling of the GPI precursor molecules before they are transferred to protein in the endoplasmic reticulum. The genes encoding the requisite phospholipase A2 and A1 activities for this remodeling have thus far been elusive. Here, we identify a gene, Tb927.7.6110, that encodes a protein that is both necessary and sufficient for GPI-phospholipase A2 (GPI-PLA2) activity in the procyclic form of the parasite. The predicted protein product belongs to the alkaline ceramidase, PAQR receptor, Per1, SID-1, and TMEM8 (CREST) superfamily of transmembrane hydrolase proteins and shows sequence similarity to Post-GPI-Attachment to Protein 6 (PGAP6), a GPI-PLA2 that acts after transfer of GPI precursors to protein in mammalian cells. We show the trypanosome Tb927.7.6110 GPI-PLA2 gene resides in a locus with two closely related genes Tb927.7.6150 and Tb927.7.6170, one of which (Tb927.7.6150) most likely encodes a catalytically inactive protein. The absence of GPI-PLA2 in the null mutant procyclic cells not only affected fatty acid remodeling but also reduced GPI anchor sidechain size on mature GPI-anchored procyclin glycoproteins. This reduction in GPI anchor sidechain size was reversed upon the re-addition of Tb927.7.6110 and of Tb927.7.6170, despite the latter not encoding GPI precursor GPI-PLA2 activity. Taken together, we conclude that Tb927.7.6110 encodes the GPI-PLA2 of GPI precursor fatty acid remodeling and that more work is required to assess the roles and essentiality of Tb927.7.6170 and the presumably enzymatically inactive Tb927.7.6150.

Inhibition of translation termination by the antimicrobial peptide Drosocin.

The proline-rich antimicrobial peptide (PrAMP) Drosocin (Dro) from fruit flies shows sequence similarity to other PrAMPs that bind to the ribosome and inhibit protein synthesis by varying mechanisms. The target and mechanism of action of Dro, however, remain unknown. Here we show that Dro arrests ribosomes at stop codons, probably sequestering class 1 release factors associated with the ribosome. This mode of action is comparable to that of apidaecin (Api) from honeybees, making Dro the second member of the type II PrAMP class. Nonetheless, analysis of a comprehensive library of endogenously expressed Dro mutants shows that the interactions of Dro and Api with the target are markedly distinct. While only a few C-terminal amino acids of Api are critical for binding, the interaction of Dro with the ribosome relies on multiple amino acid residues distributed throughout the PrAMP. Single-residue substitutions can substantially enhance the on-target activity of Dro.

Molecular characterization of a novel victorivirus (order Ghabrivirales, family Totiviridae) infecting Metarhizium anisopliae.

Here, we report the occurrence and complete genome sequence of a novel victorivirus infecting Metarhizium anisopliae, named "Metarhizium anisopliae victorivirus 1" (MaVV1). The genome is 5353 bp in length and contains two open reading frames (ORFs), encoding a coat protein and an RNA-dependent RNA polymerase (RdRp), that overlap at the octanucleotide sequence AUGAGUAA. These ORFs showed sequence similarity to the corresponding ORFs of Ustilaginoidea virens RNA virus L (68.23%) and Ustilaginoidea virens RNA virus 13 (58.11%), respectively, both of which belong to the family Totiviridae. Phylogenetic analysis based on RdRp sequences revealed that MaVV1 clustered with members of the genus Victorivirus. This is the first genome sequence reported for a virus belonging to the genus Victorivirus infecting the entomopathogenic fungus M. anisopliae.

The role of conserved amino acid residues of Sae3 in Mei5-Sae3 complex for Dmc1 assembly in meiotic recombination.

Meiotic recombination between homologous chromosomes is promoted by the collaborative action of two RecA homologs, Rad51 and meiosis-specific Dmc1. The filament assembly of Dmc1 is promoted by meiosis-specific Mei5-Sae3 in budding yeast. Mei5-Sae3 shows sequence similarity to fission yeast Sfr1-Swi5, which stimulates DNA strand exchanges by Rad51 as well as Dmc1. Sae3 and Swi5 share a conserved motif with the amino acid sequence YNEI/LK/RD. In this study, we analyzed the role of the YNEL residues in the Sae3 sequence in meiotic recombination and found that these residues are critical for Sae3 function in Dmc1 assembly. L59 substitution in the Sae3 protein disrupts complex formation with Mei5, while Y56 and N57 substitutions do not. These observations reveal the differential contribution of conserved YNEL residues to Sae3 activities in meiotic recombination.

Mechanistic Studies on Dehydration in Class V Lanthipeptides.

Lanthipeptides are ribosomally synthesized and post-translationally modified peptides characterized by lanthionine (Lan) and/or methyllanthionine (MeLan) residues. Four classes of enzymes have been identified to install these structures in a substrate peptide. Recently, a novel class of lanthipeptides was discovered that lack genes for known class I–IV lanthionine synthases in their biosynthetic gene cluster (BGC). In this study, the dehydration of Ser/Thr during the biosynthesis of the class V lanthipeptide cacaoidin was reconstituted in vitro. The aminoglycoside phosphotransferase-like enzyme CaoK iteratively phosphorylates Ser/Thr residues on the precursor peptide CaoA, followed by phosphate elimination catalyzed by the HopA1 effector-like protein CaoY to achieve eight successive dehydrations. CaoY shows sequence similarity to the OspF family proteins and the lyase domains of class III/IV lanthionine synthetases, and mutagenesis studies identified residues that are critical for catalysis. An AlphaFold prediction of the structure of the dehydration enzyme complex engaged with its substrate suggests the importance of hydrophobic interactions between the CaoA leader peptide and CaoK in enzyme–substrate recognition. This model is supported by site-directed mutagenesis studies.

Vexitoxins: conotoxin-like venom peptides from predatory gastropods of the genus Vexillum.

Venoms of predatory marine cone snails are intensely studied because of the biomedical applications of the neuropeptides that they contain, termed conotoxins. Meanwhile some gastropod lineages have independently acquired secretory glands strikingly similar to the venom gland of cone snails, suggesting that they possess similar venoms. Here we focus on the most diversified of these clades, the genus Vexillum. Based on the analysis of a multi-species proteo-transcriptomic dataset, we show that Vexillum species indeed produce complex venoms dominated by highly diversified short cysteine-rich peptides, vexitoxins. Vexitoxins possess the same precursor organization, display overlapping cysteine frameworks and share several common post-translational modifications with conotoxins. Some vexitoxins show sequence similarity to conotoxins and adopt similar domain conformations, including a pharmacologically relevant inhibitory cysteine knot motif. The Vexillum envenomation gland (gL) is a notably more recent evolutionary novelty than the conoidean venom gland. Thus, we hypothesize lower divergence between vexitoxin genes, and their ancestral ‘somatic’ counterparts compared to that in conotoxins, and we find support for this hypothesis in the evolution of the vexitoxin cluster V027. We use this example to discuss how future studies on vexitoxins can inform the origin of conotoxins, and how they may help to address outstanding questions in venom evolution.