Low Molecular Weight Subunits Research Articles

A monoclonal antibody collection for C. difficile typing ?

Clostridioides difficile is the leading cause of antibiotic-associated diarrhea and pseudomembranous colitis in adults. Various C. difficile strains circulate currently, associated with different outcomes and antibiotic resistance profiles. However, most studies still focus on the reference strain 630 that does not circulate anymore, partly due to the lack of immunological tools to study current clinically important C. difficile PCR ribotypes. The goal of this study was to generate monoclonal antibodies recognizing various epidemic ribotypes of C. difficile. To do so, we immunized mice expressing human variable antibody genes with the Low Molecular Weight (LMW) subunit of the surface layer protein SlpA from various C. difficile strains. Monoclonal antibodies purified from hybridomas bound LMW with high-affinity and whole bacteria from current C. difficile ribotypes with different cross-specificities. This first collection of anti-C. difficile mAbs represent valuable tools for basic and clinical research.

#5339 TRANSTHYRETIN AMYLOIDOSIS WITH BIOPSY PROVEN RENAL INVOLVEMENT

Abstract Background and Aims Systemic amyloidosis is a cluster of disorders characterized by tissue deposition of amyloid (highly ordered fibrils composed of low molecular weight subunits of a variety of proteins). Transthyretin (TTR) amyloidosis (ATTR) is either an autosomal dominant inherited condition (ATTRv, where v stands for “variant”) or a non hereditary disease due to misfolding of wild-type TTR (ATTRwt). ATTR is likely underdiagnosed due to its clinical variability and lack of specific symptoms or biomarkers. The first aim of the study is to emphasise the importance of suspecting ATTR when facing certain clinical manifestations in association with renal impairment and urinary abnormalities. Furthermore, renal biopsy provides crucial information for a correct diagnosis and treatment approach. Method We report 5 cases of biopsy-proven renal ATTR deposition in patients presenting with mild to moderate renal impairment and mild urinary abnormalities. The TTR precursor has been confirmed in kidney specimens by immunohistochemistry. Genotyping was carried out in every patient. Results The presence of amyloid was found in all patients, with different distribution (#1-3 pericapsular and vascular; #2 vascular; #4 mesangial, vascular, in tubular basement membrane and in the interstitium of cortex and medulla; #5 pericapsular, vascular and interstitial). On genetic analysis three patients were wild-type (#1-2-5), one carried the c.424G>A (p.(Val142Ile)) mutation (#3) and the last one the Val30Met mutation (#4). Conclusion Suspicion of ATTR should be considered in patients with increase in serum creatinine, mild proteinuria and cardiac and peripheral nerve symptoms. This can be of utmost importance in elderly patients in whom a monoclonal gammopathy of undetermined significance can co-exist and drive a wrong diagnosis of primary light chain amyloidosis (AL), that could lead the clinician to undertake inappropriate treatments. Renal biopsy and genetic sequencing are both critical in diagnosing ATTR. Finally, we suggest distinguishing in the context of the ATTR deposition disease an ATTR nephropathy characterized by mesangial accumulation of amyloid, that impacts functional and urinary assessment, from isolated deposition in small vessels without specific clinical consequences, albeit critical for ATTR diagnosis.

Successful Diflunisal Desensitization in a Transthyretin Amyloidosis Patient With Ibuprofen Allergy: A Case Report

Background: Amyloid diseases are hereditary and include transthyretin (TTR) amyloidosis where subunit protein mutations may occur in genes for TTR, leading to the deposition of fibrils (low molecular weight subunits (5 to 25 KD of proteins) in extracellular tissues. By reducing the formation of TTR amyloid, diflunisal, a nonsteroidal anti-inflammatory drug, can preserve the quality of life and significantly reduce disease progression. We present a case of a 61-year-old male patient with a history of ibuprofen allergy, diagnosed with TTR amyloidosis, complicated with peripheral neuropathy, cardiac, and liver amyloid. He developed bilateral mild eye swelling from the ibuprofen oral provocation test. With a similar structural backbone of carboxylic acid, he could develop pseudoallergy to diflunisal with an unknown likelihood of developing an allergic reaction.
 Objectives: This study aims to design successful diflunisal desensitization in a patient with TTR amyloidosis.
 Methods: The patient underwent a 14-step diflunisal desensitization procedure using 2 tablets of diflunisal 500 mg that was dissolved in 40 mL of sodium bicarbonate 8.4% injection to create serial 10-fold dilutions. Oral desensitization was administered in the escalation of the doses at 30-min intervals, with a starting dose of 0.1 mg until a final dose of 250 mg was reached.
 Results: The patient tolerated diflunisal desensitization and was continued on diflunisal treatment without any evidence of an allergic reaction.
 Conclusion: Diflunisal desensitization can be considered in patients with a history of ibuprofen allergy if there are no available alternative treatments. To the best of our knowledge, this is the first article describing a patient with angioedema to ibuprofen who could tolerate oral diflunisal after desensitization.

Receptor binding protein of prophage reversibly recognizes the low-molecular weight subunit of the surface-layer protein SlpA in Clostridioides difficile.

Receptor-binding proteins (RBPs) are located at the viral tail and mediate the initial recognition of phage to a specific bacterial host. Phage RBPs have co-evolved with numerous types of host receptors resulting in the formation of a diverse assortment of cognate pairs of RBP-receptors that function during the phage attachment step. Although several Clostridioides difficile bacteriophages have been discovered, their RBPs are poorly described. Using homology analysis, putative prophage-tail structure (pts) genes were identified from the prophage genome of the C. difficile HN10 strain. Competition and enzyme-linked immunosorbent assays, using recombinant PtsHN10M, demonstrated the interaction of this Pts to C. difficile cells, suggesting a role as a phage RBP. Gel filtration and cross-linking assay revealed the native form of this protein as a homotrimer. Moreover, truncated variants indicated that the C-terminal domain of PtsHN10M was important for binding to C. difficile cells. Interaction of PtsHN10M was also observed to the low-molecular weight subunit of surface-layer protein A (SlpA), located at the outermost surface of C. difficile cells. Altogether, our study highlights the function of PtsHN10M as an RBP and potentially paves the way toward phage engineering and phage therapy against C. difficile infection.

Pasting properties of high-amylose wheat in conventional and high-temperature Rapid Visco Analyzer: Molecular contribution of starch and gluten proteins

The popularity of high-amylose cultivars of main crops (e.g., high-amylose wheat, HAW) has been increasing because of their unique functional properties and enhanced nutritional values. In the current study, we employed the high-temperature Rapid Visco-Analyzer (HTRVA) to evaluate the performance of HAW flours and starches with an extensive range of amylose contents under high-temperature processing. The pasting parameters, total setback viscosity (TSV) and final viscosity (FV) from HTRVA, did not significantly correlate ( p > 0.05) with those from conventional RVA. The results indicate that conventional RVA could not robustly predict the pasting behaviours of HAW ingredients at high-temperature processing (partially due to different extent of starch disruption and leaching). The amylose content by iodine colorimetry method was not a good indicator of the cooling and retrogradation process of HAW flour and starch after high-temperature heating, with low R 2 values of the linear regression of TSV and FV on amylose content. However, TSV and FV of HAW flours as analysed by HTRVA negatively correlate ( p < 0.01) with wheat flour protein content, as well as with the abundance of glutenin (low molecular weight subunit, p < 0.05) as identified by a SWATH-MS (Sequential Window Acquisition of all Theoretical Mass Spectra) proteomics method. The protein attributes could contribute to restricting both swelling of granules during heating and the reassociation of starch polymers during cooling. Amylose (AM) and amylopectin (AP) fine structural features also regulate pasting behaviours. In particular, longer amylopectin outer chains promote peak viscosity, while larger amylose (whole) molecules have the opposite effect. This study presents new insights into the molecular basis for the pasting behaviours of HAW in conventional and high-temperature RVA. • High-temperature RVA profiles were compared to conventional RVA profiles. • High heating temperature reduced holding strength and final viscosity. • Peak viscosity was increased by longer AP outer chains but reduced by larger AM. • Total protein did not correlate with high temperature or conventional RVA parameters. • Detailed glutenin profiles (e.g., LMW-GS) show correlations with pasting parameters.

Secondary Amyloidosis with Fatal Outcome in a Child with Meningomyelocele

Amyloidosis constitutes a group of diseases characterized by extracellular deposition of fibrils composed of low molecular weight subunits of a variety of proteins. Secondary amyloidosis may result from chronic inflammatory conditions such as familial Mediterranean fever, juvenile idiopathic arthritis, tuberculosis, and bronchiectasis. Myelomeningocele is reported rarely in literature as a cause of amyloidosis. We report here a case of 6-year-old boy with operated congenital lumbar myelomeningocele with paraparesis and neurogenic bladder, who was diagnosed with nephrotic syndrome with hypertension. He underwent a renal biopsy which showed amyloidosis. During the course of treatment, he acquired a perigenital infection and later succumbed to it. A closer follow-up of patients with neurogenic bladder can help identify and manage renal complications early.

The PsbJ protein is required for photosystem II activity in centers lacking the PsbO and PsbV lumenal subunits.

Photosystem II (PS II) of oxygenic photosynthesis is found in the thylakoid membranes of plastids and cyanobacteria. The mature PS II complex comprises a central core of four membrane proteins that bind the majority of the redox-active cofactors. In cyanobacteria the central core is surrounded by 13 low-molecular-weight (LMW) subunits which each consist of one or two transmembrane helices. Three additional hydrophilic subunits known as PsbO, PsbU and PsbV are found associated with hydrophilic loops belonging to the core proteins protruding into the thylakoid lumen. During biogenesis the majority of the LMW subunits are known to initially associate with individual pre-assembly complexes consisting of one or more of the core proteins; however, the point at which the PsbJ LMW subunit binds to PS II is not known. The majority of models for PS II biogenesis propose that the three extrinsic proteins and PsbJ bind in the final stages of PS II assembly. We have investigated the impact of creating the double mutants ∆PsbJ:∆PsbO, ∆PsbJ:∆PsbU and ∆PsbJ:∆PsbV to investigate potential cooperation between these subunits in the final stages of biogenesis. Our results indicate that PsbJ can bind to PS II in the absence of any one of the extrinsic proteins. However, unlike their respective single mutants, the ∆PsbJ:∆PsbO and ∆PsbJ:∆PsbV strains were not photoautotrophic and were unable to support oxygen evolution suggesting a functional oxygen-evolving complex could not assemble in these strains. In contrast, the PS II centers formed in the ∆PsbJ:∆PsbU strain were capable of photoautotrophic growth and could support oxygen evolution when whole-chain electron transport was supported by the addition of bicarbonate.

Isolation, Substrate Specificity, and Subunit Characterization of the Xylanosomes Produced by Oerskovia turbata JCM 3160.

This work aims at functional studies of the multienzyme complexes produced by Oerskovia turbata JCM 3160 and reveal of their subunit structures. The multienzyme complexes were isolated, enzymatic assayed, the whole genome sequence was determined in fine scale, and the subunit structure was identified by Maldi-TOF mass spectrometry. The isolated multienzyme complexes here show similar particle size with the xylanosomes produced by Cellulosimicrobium cellulans F16, have at least two conserved multi-domain proteins, while differ significantly in enzymatic activities and low molecular weight subunit compositions. This is the first report of the enzymatic activities and subunit structures of xylanosome produced by Oerskovia turbata, providing insights into its diverse capability as well as degrading bias on hemicelluloses.

Effect of HMW and LMW glutenin alleles on quality traits of bread wheat

This study was performed to investigate impact of HMW and LMW glutenin alleles on quality traits of bread wheat cultivars. Fifteen bread wheat varieties were used for field trails during 2012-13 and 2013-14 under irrigated conditions of Diyarbak?r and Mardin locations, Turkey. We investigated the quality of varieties that have same HMW-GS (High molecular weight subunits) and different LMW-GS (Low molecular weight subunits) or vice versa. Results indicated that GluA3-c &gt; d &gt; e, GluB3-g &gt; b? = i, and GluD3-b ? c &gt; a for LMW-GS, and GluB1-7+8 &gt; GluB1-17+18; GluD1-5+10 &gt; GluD1-2+12 for HMW-GS have higher extensograph dough energy, extensibility, resistance, also higher farinograph stability time, gluten index and grain hardness values. The overall evaluation of the results obtained from this study demonstrated that GluA1-1 or 2

Isolation and subunit structure of the xylanosome complex produced by Actinotalea fermentans JCM9966.

Xylanosomes, also known as hemicellulosomes, are hemicellulose-degrading nano-scale multienzyme complexes produced by some Firmicutes, Actinobacteria, and Fungi. Here we report the isolation of the MECs produced by Actinotalea fermentas JCM9966, as well as the functional studies and subunit structure revealed by proteomic identifications. The isolated MECs here shows similar particle size with the xylanosomes produced by C. cellulans F16, have several conserved multi-domain proteins, while differ significantly in enzymatic activities and low molecular weight subunit compositions, indicating diverse capability as well as bias in degrading hemicelluloses.

Dodecameric structure of a small heat shock protein from Mycobacterium marinum M.

Small heat shock proteins (sHSPs) are ATP-independent molecular chaperones present ubiquitously in all kingdoms of life. Their low molecular weight subunits associate to form higher order structures. Under conditions of stress, sHSPs prevent aggregation of substrate proteins by undergoing rapid changes in their conformation or stoichiometry. Polydispersity and dynamic nature of these proteins have made structural investigations through crystallography a daunting task. In pathogens like Mycobacteria, sHSPs are immuno-dominant antigens, enabling survival of the pathogen within the host and contributing to disease persistence. We characterized sHSPs from Mycobacterium marinum M and determined the crystal structure of one of these. The protein crystallized in three different conditions as dodecamers, with dimers arranged in a tetrahedral fashion to form a closed cage-like architecture. Interestingly, we found a pentapeptide bound to the dodecamers revealing one of the modes of sHSP-substrate interaction. Further, we have observed that ATP inhibits the chaperoning activity of the protein.

The P-class pentatricopeptide repeat protein PpPPR_21 is needed for accumulation of the psbI-ycf12 dicistronic mRNA in Physcomitrella chloroplasts.

Chloroplast gene expression is controlled by numerous nuclear-encoded RNA-binding proteins. Among these, pentatricopeptide repeat (PPR) proteins are known to be key players in post-transcriptional regulation in chloroplasts. However, the functions of many PPR proteins remain unknown. In this study, we characterized the function of a chloroplast-localized P-class PPR protein PpPPR_21 in Physcomitrella patens. Knockout (KO) mutants of PpPPR_21 exhibited reduced protonemata growth and lower photosynthetic activity. Immunoblot analysis and blue-native gel analysis showed a remarkable reduction of the photosystem II (PSII) reaction center protein and poor formation of the PSII supercomplexes in the KO mutants. To assess whether PpPPR_21 is involved in chloroplast gene expression, chloroplast genome-wide microarray analysis and Northern blot hybridization were performed. These analyses indicated that the psbI-ycf12 transcript encoding the low molecular weight subunits of PSII did not accumulate in the KO mutants while other psb transcripts accumulated at similar levels in wild-type and KO mutants. A complemented PpPPR_21KO moss transformed with the cognate full-length PpPPR_21cDNA rescued the level of accumulation of psbI-ycf12 transcript. RNA-binding experiments showed that the recombinant PpPPR_21 bound efficiently to the 5' untranslated and translated regions of psbImRNA. The present study suggests that PpPPR_21 may be essential for the accumulation of a stable psbI-ycf12mRNA.

Nitrogen topdressing timing modifies free amino acids profiles and storage protein gene expression in wheat grain

BackgroundNitrogen is one basic element of amino acids and grain protein in wheat. In field experiments, wheat plants were subjected to different timing of nitrogen topdressing treatments: at the stages of emergence of the top fifth leaf (TL5), top third leaf (TL3) and top first leaf (TL1) to test the regulatory effects of nitrogen topdressing timing on grain protein quality. The underlying mechanisms were elucidated by clarifying the relationship between proteolysis in vegetative organs and accumulation of amino acids in the endosperm cavity, conversion of amino acids, and storage protein synthesis in endosperm of wheat grain.ResultsDelayed nitrogen topdressing up-regulated gene expression related to nitrogen metabolism and protease synthesis in the flag leaf, followed by more free amino acids being transported to both the cavity and the endosperm from 7 days after anthesis (DAA) to 13 DAA in TL1. TL1 enhanced the conversion between free amino acids in endosperm and upregulated the expression of genes encoding high molecular weight (HMW) and low molecular weight (LMW) subunits and protein disulfide isomerases-like (PDIL) proteins, indicating that the synthesis and folding of glutenin were enhanched by delayed nitrogen topdressing. As a consequense, the content of glutenin macropolymers (GMP) and glutenin increased with delaying nitrogen topdressing.ConclusionsThe results highlight the relationship between nitrogen remobilization and final grain protein production and suggest that the nitrogen remobilization processes could be a potential target for improving the quality of wheat grain. Additionally, specific gene expression related to nitrogen topdressing was identified, which conferred more detailed insights into underlying mechanism on the modification protein quality.

FEATURES OF THE SITUATION OF THE IMMUNE SYSTEM IN WOMEN WITH UTERINE LEIOMYOMA AFTER EMBOLIZATION OF UTERINE ARTERIES

One of the most effective treatment for uterine leiomyomas is uterine artery embolization. However, its impact on the immune system of women is still insufficiently studied.The aim of the study- to investigate the state of non-specific and specific cells of cellular immunity in women with uterine leiomyoma after embolization of uterine arteries, depending on the peculiarities of the post-embolisation period.Material and methods of research - For the purpose of conducting immunological studies, whole peripheral blood and its serum of women with leiomyoma of the uterus were used before and after the embolization of the uterine arteries.The article presents: Evaluation of nonspecific and specific components of cellular immunity in women with uterine leiomyoma one month after the uterine arteries embolization did not reveal any significant changes compared with the indicators before it was performed. It may attest the safety of this intervention. However women with inflammatory complications after UAE usually have abnormal function of phagocytes and T-cellular immunity, as well as the level of circulating immune complexes, mainly due to low molecular weight subunits, which have a damaging effect on the endothelium of the vessels.Conclusion. On the basis of the obtained data, it can be argued that patients with uterine leiomyoma who are planning to embryo uterine arteries are advised to carry out the prevention of inflammatory complications after intervention in order to reduce the likelihood of changes in the immune system.

Effect of different doses of nitrogen on protein profiling, pasting and quality attributes of rice from different cultivars

Effect of different level (60, 120 and 180kgN/ha) of nitrogen (N) application on protein profiling, pasting and cooking quality characteristics of milled rice from different paddy cultivars was evaluated. N dose showed positive correlation with protein content and negative correlation with L*, whiteness and amylose content. N application significantly affected the protein profile, textural and pasting properties of different cultivars. All the cultivars expect PR120 and PAU201, showed an increase in the amount of accumulation of 60kDa polypeptide with increase in N application. Accumulation of prolamines (16 and 14kDa) and polypeptides of 38 and 35kDa increased in all the cultivars. Size exclusion chromatography revealed decrease in low molecular weight subunits and increase in medium molecular weight subunits in all the cultivars upon N application. However, high molecular weight subunits increased in IET21214 and decreased in PR120 and PAU20 upon N application. N application resulted in increase in glutelins and decrease in peak and breakdown viscosity. PAU201 and PR120 showed lower AAC due to low accumulation of 60kDa granule-bound starch synthase (GBSS), in response to N application. Gumminess and hardness of cooked rice increased with the increase in N dose and the increase was significant at 60kgN/ha.

Transthyretin amyloidosis: an over review

Amyloidosis refers to the extracellular deposition of fibrils that are composed of low molecular weight subunits of a variety of serum proteins. The most common familial amyloidosis is caused by the transthyretin protein. People who are born with inherited mutations in the transthyretin gene produce abnormal, (“variant”) transthyretin throughout their liver. The clinical manifestations vary, depending upon the particular substitution, but result either in neuropathy, cardiomyopathy, or both. One of the most common hereditary transthyretin amyloid cardiomyopathies is caused by the Val122IIe mutation. Progressive amyloid deposition in the myocardium and/or in the electrical conduction system is responsible for restrictive cardiomyopathy and unpredictable episodes of arrhythmias and/or severe conduction disorders. The vast majority of transthyretin-familial amyloidotic polyneuropathy cases are associated with Val30Met mutation. The main neuropathic feature of transthyretin amyiloidosis is a progressive sensorimotor and autonomic neuropathy. The first step in evaluating a patient with transthyretin amyloidosis consists in establishing the diagnosis and then evaluating the extent of disease. Deposition of amyloid via tissue can be demonstrated by Congo red staining of biopsy specimens. In all cases, amyloid typing has to be completed by transthyretin gene sequencing and by immunofixation electrophoresis of serum and urine. Current treatment options for patients with transthyretin amyiloidosis are limited. For patients with transthyretin-primary familial amyloidosis who have mild or moderate disease and a diagnosis confirmed by genetic testing and biopsy, liver transplant is the current standard of care.

Targeting surface-layer proteins with single-domain antibodies: a potential therapeutic approach against Clostridium difficile-associated disease.

Clostridium difficile is a leading cause of death from gastrointestinal infections in North America. Antibiotic therapy is effective, but the high incidence of relapse and the rise in hypervirulent strains warrant the search for novel treatments. Surface layer proteins (SLPs) cover the entire C. difficile bacterial surface, are composed of high-molecular-weight (HMW) and low-molecular-weight (LMW) subunits, and mediate adherence to host cells. Passive and active immunization against SLPs has enhanced hamster survival, suggesting that antibody-mediated neutralization may be an effective therapeutic strategy. Here, we isolated a panel of SLP-specific single-domain antibodies (VHHs) using an immune llama phage display library and SLPs isolated from C. difficile hypervirulent strain QCD-32g58 (027 ribotype) as a target antigen. Binding studies revealed a number of VHHs that bound QCD-32g58 SLPs with high affinity (KD = 3–6 nM) and targeted epitopes located on the LMW subunit of the SLP. The VHHs demonstrated melting temperatures as high as 75 °C, and a few were resistant to the gastrointestinal protease pepsin at physiologically relevant concentrations. In addition, we demonstrated the binding specificity of the VHHs to the major C. difficile ribotypes by whole cell ELISA, where all VHHs were found to bind 001 and 027 ribotypes, and a subset of antibodies were found to be broadly cross-reactive in binding cells representative of 012, 017, 023, and 078 ribotypes. Finally, we showed that several of the VHHs inhibited C. difficile QCD-32g58 motility in vitro. Targeting SLPs with VHHs may be a viable therapeutic approach against C. difficile-associated disease.Electronic supplementary materialThe online version of this article (doi:10.1007/s00253-015-6594-1) contains supplementary material, which is available to authorized users.

Gluten Alleles and Predicted Dough Quality for Wheat Varieties Worldwide: A Great Resource—Free on the AACC International Website

The gluten composition of more than 8,500 wheat varieties is provided in two new databases on the AACC International website (www.aaccnet.org/initiatives/definitions/Pages/Gluten.aspx). The databases augment earlier versions (1–3) by providing a program to screen the large volume of data. For each variety, the program provides the gliadin composition, listed as alleles at the Gli-1 and Gli-2 loci; the high molecular weight subunits of glutenin (HMW-GS), as subunit numbers and alleles at the Glu-1 loci; the low molecular weight subunits of glutenin (LMW-GS), as alleles at the Glu-3 loci; the Payne Glu-1 scores for dough quality; and estimates of dough strength (as Rmax) and extensibility based on both HMW-GS and LMW-GS alleles.

Cloning and Characterization of Three Genes Encoding LMW-GSs from &lt;i&gt;Triticum aestivum&lt;/i&gt;, Cultival Cheyenne

Three low molecular weight subunit genes, named LMW-CND1 (GeneBank accession JQ780048), LMW-CND2 (GeneBank accession JQ779840), LMW-CND3 (GeneBank accession JQ779841), with a ORF of 1053 bp, 903 bp, 969 bp, respectively, were isolated from cv. Cheyenne and characterized detailed in molecular level. The proteins encoded by the genes, with 350, 300, 322 amino acid residues respectively, differ only in repetitive domain of sequences due to insertion or deletion of repeats in this domain. Highly similarity in amino-acid sequence between these three subunits and other published LMW-GSs was also observed, showing that all three genes published here are typical LMW-GS genes and closely related to the genes on chromosome 1D. Besides, secondary structure prediction of proteins indicated that, in the three LMW-GSs, random loop accounts for no less than 70 %, α-helix amounts to 26 %, average, and only 1.4 %~1.7 % is β-sheet.

Deletion of psbJ leads to accumulation of Psb27–Psb28 photosystem II complexes in Thermosynechococcus elongatus

The life cycle of Photosystem II (PSII) is embedded in a network of proteins that guides the complex through biogenesis, damage and repair. Some of these proteins, such as Psb27 and Psb28, are involved in cofactor assembly for which they are only transiently bound to the preassembled complex. In this work we isolated and analyzed PSII from a ΔpsbJ mutant of the thermophilic cyanobacterium Thermosynechococcus elongatus. From the four different PSII complexes that could be separated the most prominent one revealed a monomeric Psb27–Psb28 PSII complex with greatly diminished oxygen-evolving activity. The MALDI-ToF mass spectrometry analysis of intact low molecular weight subunits (<10kDa) depicted wild type PSII with the absence of PsbJ. Relative quantification of the PsbA1/PsbA3 ratio by LC-ESI mass spectrometry using 15N labeled PsbA3-specific peptides indicated the complete replacement of PsbA1 by the stress copy PsbA3 in the mutant, even under standard growth conditions (50μmol photons m−2 s−1). This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.