Substrate Specificity Of Protease Research Articles

Determination of the substrate specificity of the MASP-1 protease of the complement pathway provides initial insights into potential physiological roles

Determination of the substrate specificity of the MASP-1 protease of the complement pathway provides initial insights into potential physiological roles

A comparative study on substrate specificity, activity and thermal stability of some plant proteases

A comparative study on substrate specificity, activity and thermal stability of some plant proteases

Proteases' prime targets revealed

Mass spectrometry analysis of proteome-derived peptide libraries enables high-throughput determination of protease substrate specificity.

Analysis of the minimal specificity of CED-3 using a yeast transcriptional reporter system

Determination of the substrate specificity of site-specific proteases helps define their physiological roles. We developed a yeast-based system for defining the minimal substrate specificity of site-specific proteases, within the context of a protein. Using this system, we characterized the P4–P1 substrate specificity of the nematode apoptotic caspase CED-3. Apart from an absolute requirement for aspartate at the P1 position, CED-3 is a relatively promiscuous caspase capable of cleaving substrates bearing many amino acids at P4–P2 sites.

Regulation of cuticle-degrading subtilisin proteases from the entomopathogenic fungi, Lecanicillium spp: implications for host specificity

The ability to produce cuticle-degrading proteases to facilitate host penetration does not distinguish per se entomopathogenic fungi from saprophytes. However, adapted pathogens may produce host-protein specific enzymes in response to cues. This possibility prompted an investigation of the regulation of isoforms of the subtilisin Pr1-like proteases from five aphid-pathogenic isolates of Lecanicillium spp. Significant differences were found in substrate specificity and regulation of Pr1-like proteases between isoforms of the same isolate and between different isolates. For example, the pI 8.6 isoform from KV71 was considerably more active against aphid than locust cuticle and was induced specifically by N-acetylglucosamine (NAG). Isoform pI 9.1 from the same isolate was only produced on insect cuticle while most other isoforms were more prominent on chitin containing substrates but not induced by NAG. The ability to regulate isoforms independently may allow production at critical points in host penetration. Appearance of proteases (not subtilisins) with pI 4.2 and 4.4 only on aphid cuticle was a possible link with host specificity of KV71. The absence of C or N metabolite repression in subtilisins from KV42 is unusual for pathogen proteases and may help to account for differences in virulence strategy between aphid-pathogenic isolates of Lecanicillium longisporum (unpublished data).

Elucidation of the substrate specificity of the MASP-2 protease of the lectin complement pathway and identification of the enzyme as a major physiological target of the serpin, C1-inhibitor

Complement is a central component of host defence, but unregulated activation can contribute to disease. The system can be initiated by three pathways: classical, alternative and lectin. The classical and lectin pathways are initiated by the C1 and mannose-binding lectin (MBL) or ficolin complexes, respectively, with C1s the executioner protease of the C1 complex and MASP-2 its counterpart in the lectin complexes. These proteases in turn cleave the C4 and C2 components of the system. Here we have elucidated the cleavage specificity of MASP-2 using a randomised substrate phage display library. Apart from the crucial P1 position, the MASP-2 S2 and S3 subsites (in that order) play the greatest role in determining specificity, with Gly residues preferred at P2 and Leu or hydrophobic residues at P3. Cleavage of peptide substrates representing the known physiological cleavage sequences in C2, C4 or the serpin C1-inhibitor (a likely regulator of MASP-2) revealed that MASP-2 is up to 1000 times more catalytically active than C1s. C1-inhibitor inhibited MASP-2 50-fold faster than C1s and much faster than any other protease tested to date, implying that MASP-2 is a major physiological target of C1-inhibitor.

Bioinformatic approaches for modeling the substrate specificity of HIV-1 protease: an overview

HIV-1 protease has a broad and complex substrate specificity, which hitherto has escaped a simple comprehensive definition. This, and the relatively high mutation rate of the retroviral protease, makes it challenging to design effective protease inhibitors. Several attempts have been made during the last two decades to elucidate the enigmatic cleavage specificity of HIV-1 protease and to predict cleavage of novel substrates using bioinformatic analysis methods. This review describes the methods that have been utilized to date to address this important problem and the results achieved. The data sets used are also reviewed and important aspects of these are highlighted.

OPA1 Processing Reconstituted in Yeast Depends on the Subunit Composition of them-AAA Protease in Mitochondria

The morphology of mitochondria in mammalian cells is regulated by proteolytic cleavage of OPA1, a dynamin-like GTPase of the mitochondrial inner membrane. The mitochondrial rhomboid protease PARL, and paraplegin, a subunit of the ATP-dependent m-AAA protease, were proposed to be involved in this process. Here, we characterized individual OPA1 isoforms by mass spectrometry, and we reconstituted their processing in yeast to identify proteases involved in OPA1 cleavage. The yeast homologue of OPA1, Mgm1, was processed both by PARL and its yeast homologue Pcp1. Neither of these rhomboid proteases cleaved OPA1. The formation of small OPA1 isoforms was impaired in yeast cells lacking the m-AAA protease subunits Yta10 and Yta12 and was restored upon expression of murine or human m-AAA proteases. OPA1 processing depended on the subunit composition of mammalian m-AAA proteases. Homo-oligomeric m-AAA protease complexes composed of murine Afg3l1, Afg3l2, or human AFG3L2 subunits cleaved OPA1 with higher efficiency than paraplegin-containing m-AAA proteases. OPA1 processing proceeded normally in murine cell lines lacking paraplegin or PARL. Our results provide evidence for different substrate specificities of m-AAA proteases composed of different subunits and reveal a striking evolutionary switch of proteases involved in the proteolytic processing of dynamin-like GTPases in mitochondria.

Roles of S3 Site Residues of Nattokinase on its Activity and Substrate Specificity

Nattokinase (Subtilisin NAT, NK) is a bacterial serine protease with high fibrinolytic activity. To probe their roles on protease activity and substrate specificity, three residues of S3 site (Gly(100), Ser(101) and Leu(126)) were mutated by site-directed mutagenesis. Kinetics parameters of 20 mutants were measured using tetrapeptides as substrates, and their fibrinolytic activities were determined by fibrin plate method. Results of mutation analysis showed that Gly(100) and Ser(101) had reverse steric and electrostatic effects. Residues with bulky or positively charged side chains at position 100 decreased the substrate binding and catalytic activity drastically, while residues with the same characters at position 101 could obviously enhance protease and fibrinolytic activity of NK. Mutation of Leu(126) might impair the structure of the active cleft and drastically decreased the activity of NK. Kinetics studies of the mutants showed that S3 residues were crucial to keep protease activity while they moderately affected substrate specificity of NK. The present study provided some original insight into the P3-S3 interaction in NK and other subtilisins, as well as showed successful protein engineering cases to improve NK as a potential therapeutic agent.

Structural evidence for regulation and specificity of flaviviral proteases and evolution of the Flaviviridae fold

Pathogenic members of the flavivirus family, including West Nile Virus (WNV) and Dengue Virus (DV), are growing global threats for which there are no specific treatments. The two-component flaviviral enzyme NS2B-NS3 cleaves the viral polyprotein precursor within the host cell, a process that is required for viral replication. Here, we report the crystal structure of WNV NS2B-NS3pro both in a substrate-free form and in complex with the trypsin inhibitor aprotinin/BPTI. We show that aprotinin binds in a substrate-mimetic fashion in which the productive conformation of the protease is fully formed, providing evidence for an "induced fit" mechanism of catalysis and allowing us to rationalize the distinct substrate specificities of WNV and DV proteases. We also show that the NS2B cofactor of WNV can adopt two very distinct conformations and that this is likely to be a general feature of flaviviral proteases, providing further opportunities for regulation. Finally, by comparing the flaviviral proteases with the more distantly related Hepatitis C virus, we provide insights into the evolution of the Flaviviridae fold. Our work should expedite the design of protease inhibitors to treat a range of flaviviral infections.

Aspartic protease activities of schistosomes cleave mammalian hemoglobins in a host-specific manner

We examined the efficiency of digestion of hemoglobin from four mammalian species, human, cow, sheep, and horse by acidic extracts of mixed sex adults of Schistosoma japonicum and S. mansoni. Activity ascribable to aspartic protease(s) from S. japonicum and S. mansoni cleaved human hemoglobin. In addition, aspartic protease activities from S. japonicum cleaved hemoglobin from bovine, sheep, and horse blood more efficiently than did the activity from extracts of S. mansoni. These findings support the hypothesis that substrate specificity of hemoglobin-degrading proteases employed by blood feeding helminth parasites influences parasite host species range; differences in amino acid sequences in key sites of the parasite proteases interact less or more efficiently with the hemoglobins of permissive or non-permissive hosts.

Cleavage preference distinguishes the two-component NS2B–NS3 serine proteinases of Dengue and West Nile viruses

Regulated proteolysis of the polyprotein precursor by the NS2B-NS3 protease is required for the propagation of infectious virions. Unless the structural and functional parameters of NS2B-NS3 are precisely determined, an understanding of its functional role and the design of flaviviral inhibitors will be exceedingly difficult. Our objectives were to define the substrate recognition pattern of the NS2B-NS3 protease of West Nile and Dengue virises (WNV and DV respectively). To accomplish our goals, we used an efficient, 96-well plate format, method for the synthesis of 9-mer peptide substrates with the general P4-P3-P2-P1-P1'-P2'-P3'-P4'-Gly structure. The N-terminus and the constant C-terminal Gly of the peptides were tagged with a fluorescent tag and with a biotin tag respectively. The synthesis was followed by the proteolytic cleavage of the synthesized, tagged peptides. Because of the strict requirement for the presence of basic amino acid residues at the P1 and the P2 substrate positions, the analysis of approx. 300 peptide sequences was sufficient for an adequate representation of the cleavage preferences of the WNV and DV proteinases. Our results disclosed the strict substrate specificity of the WNV protease for which the (K/R)(K/R)R/GG amino acid motifs was optimal. The DV protease was less selective and it tolerated well the presence of a number of amino acid residue types at either the P1' or the P2' site, as long as the other position was occupied by a glycine residue. We believe that our data represent a valuable biochemical resource and a solid foundation to support the design of selective substrates and synthetic inhibitors of flaviviral proteinases.

Influence of Charge Distribution at the Active Site Surface on the Substrate Specificity of Human Neutrophil Protease 3 and Elastase: A KINETIC AND MOLECULAR MODELING ANALYSIS

The biological functions of human neutrophil protease 3 (Pr3) differ from those of neutrophil elastase despite their close structural and functional resemblance. Although both proteases are strongly cationic, their sequences differ mainly in the distribution of charged residues. We have used these differences in electrostatic surface potential in the vicinity of their active site to produce fluorescence resonance energy transfer (FRET) peptide substrates for investigating individual Pr3 subsites. The specificities of subsites S5 to S3' were investigated both kinetically and by molecular dynamic simulations. Subsites S2, S1', and S2' were the main definers of Pr3 specificity. Combinations of results for each subsite were used to deduce a consensus sequence that was complementary to the extended Pr3 active site and was not recognized by elastase. Similar sequences were identified in natural protein substrates such as NFkappaB and p21 that are specifically cleaved by Pr3. FRET peptides derived from these natural sequences were specifically hydrolyzed by Pr3 with specificity constants k(cat)/K(m) in the 10(6) m(-1) s(-1) range. The consensus Pr3 sequence may also be used to predict cleavage sites within putative protein targets like the proform of interleukin-18, or to develop specific Pr3 peptide-derived inhibitors, because none is available for further studies on the physiopathological function of this protease.

Altered -3 Substrate Specificity of Escherichia coli Signal Peptidase 1 Mutants as Revealed by Screening a Combinatorial Peptide Library

Signal peptidase functions to cleave signal peptides from preproteins at the cell membrane. It has a substrate specificity for small uncharged residues at -1 (P1) and aliphatic residues at the -3 (P3) position. Previously, we have reported that certain alterations of the Ile-144 and Ile-86 residues in Escherichia coli signal peptidase I (SPase) can change the specificity such that signal peptidase is able to cleave pro-OmpA nuclease A in vitro after phenylalanine or asparagine residues at the -1 position (Karla, A., Lively, M. O., Paetzel, M. and Dalbey, R. (2005) J. Biol. Chem. 280, 6731-6741). In this study, screening of a fluorescence resonance energy transfer-based peptide library revealed that the I144A, I144C, and I144C/I86T SPase mutants have a more relaxed substrate specificity at the -3 position, in comparison to the wild-type SPase. The double mutant tolerated arginine, glutamine, and tyrosine residues at the -3 position of the substrate. The altered specificity of the I144C/I86T mutant was confirmed by in vivo processing of pre-beta-lactamase containing non-canonical arginine and glutamine residues at the -3 position. This work establishes Ile-144 and Ile-86 as key P3 substrate specificity determinants for signal peptidase I and demonstrates the power of the fluorescence resonance energy transfer-based peptide library approach in defining the substrate specificity of proteases.

Characterization of the West Nile virus protease substrate specificity and inhibitors

West Nile virus (WNV), a mosquito-borne member of Flaviviridae, is a human pathogen causing widespread disease for which there is no vaccine or chemotherapy. The two-component viral serine protease consists of a heterodimeric complex between the hydrophilic domain of the cofactor, NS2B (NS2BH) and the protease domain (NS3-pro). The protease is essential for polyprotein processing followed by assembly of viral replicase and genome replication. Therefore, the protease is an excellent target for development of antiviral therapeutics. Here, we report the expression in Escherichia coli, purification, and characterization of biochemical and kinetic properties of the WNV protease. Furthermore, we show that the WNV and the dengue virus type 2 (DENV-2) proteases are inhibited by aprotinin with inhibitor constants of 0.16 and 0.026μM, respectively. Molecular modeling of the WNV protease/aprotinin complex, based on the known crystal structures of the WNV NS2BH-N3pro and aprotinin, suggest a potentially strong interaction between the P2 Lys and the protease activator peptide, NS2BH. This conclusion based on molecular modeling is in agreement with our data of a higher kcat/Km value with the substrate, Boc-Gly-Lys-Arg-MCA than the Boc-Gly-Arg-Arg-MCA and is also consistent with the results of an earlier study that were based on substrate-based inhibitor peptides.

Probing the substrate specificity of the dengue virus type 2 NS3 serine protease by using internally quenched fluorescent peptides

The NS3 (dengue virus non-structural protein 3) serine protease of dengue virus is an essential component for virus maturation, thus representing an attractive target for the development of antiviral drugs directed at the inhibition of polyprotein processing. In the present study, we have investigated determinants of substrate specificity of the dengue virus NS3 protease by using internally quenched fluorogenic peptides containing Abz (o-aminobenzoic acid; synonymous to anthranilic acid) and 3-nitrotyrosine (nY) representing both native and chimaeric polyprotein cleavage site sequences. By using this combinatorial approach, we were able to describe the substrate preferences and determinants of specificity for the dengue virus NS2B(H)-NS3pro protease. Kinetic parameters (kcat/K(m)) for the hydrolysis of peptide substrates with systematic truncations at the prime and non-prime side revealed a length preference for peptides spanning the P4-P3' residues, and the peptide Abz-RRRRSAGnY-amide based on the dengue virus capsid protein processing site was discovered as a novel and efficient substrate of the NS3 protease (kcat/K(m)=11087 M(-1) x s(-1)). Thus, while having confirmed the exclusive preference of the NS3 protease for basic residues at the P1 and P2 positions, we have also shown that the presence of basic amino acids at the P3 and P4 positions is a major specificity-determining feature of the dengue virus NS3 protease. Investigation of the substrate peptide Abz-KKQRAGVLnY-amide based on the NS2B/NS3 polyprotein cleavage site demonstrated an unexpected high degree of cleavage efficiency. Chimaeric peptides with combinations of prime and non-prime sequences spanning the P4-P4' positions of all five native polyprotein cleavage sites revealed a preponderant effect of non-prime side residues on the K(m) values, whereas variations at the prime side sequences had higher impact on kcat.

The SUMO-Specific Protease SENP5 Is Required for Cell Division

Posttranslational modification of substrates by the small ubiquitin-like modifier, SUMO, regulates diverse biological processes, including transcription, DNA repair, nucleocytoplasmic trafficking, and chromosome segregation. SUMOylation is reversible, and several mammalian homologs of the yeast SUMO-specific protease Ulp1, termed SENPs, have been identified. We demonstrate here that SENP5, a previously uncharacterized Ulp1 homolog, has SUMO C-terminal hydrolase and SUMO isopeptidase activities. In contrast to other SENPs, the C-terminal catalytic domain of SENP5 preferentially processed SUMO-3 compared to SUMO-1 precursors and preferentially removed SUMO-2 and SUMO-3 from SUMO-modified RanGAP1 in vitro. In cotransfection assays, SENP5 preferentially reduced high-molecular-weight conjugates of SUMO-2 compared to SUMO-1 in vivo. Full-length SENP5 localized to the nucleolus. Deletion of the noncatalytic N-terminal domain led to loss of nucleolar localization and increased de-SUMOylation activity in vivo. Knockdown of SENP5 by RNA interference resulted in increased levels of SUMO-1 and SUMO-2/3 conjugates, inhibition of cell proliferation, defects in nuclear morphology, and appearance of binucleate cells, revealing an essential role for SENP5 in mitosis and/or cytokinesis. These findings establish SENP5 as a SUMO-specific protease required for cell division and suggest that mechanisms involving both the catalytic and noncatalytic domains determine the distinct substrate specificities of the mammalian SUMO-specific proteases.

Modulation of Infectivity in Phage Display as a Tool to Determine the Substrate Specificity of Proteases

Proteases play an important role in human and animal diseases. Rapid determination of substrate specificity is possible through the use of substrate phage display; however, current methods possess several drawbacks. They require phage-immobilization and cannot be used for infectivity-destroying or affinity tag-destroying proteases; this can make entire libraries useless. To overcome these limitations, here we introduce infectivity-modulated phage display (IMOP). IMOP uses a protease-resistant and infectivity-reducing tag fused to substrate-displaying polyvalent phages, and the specific cleavage of the substrate increases the infectivity of the phages by releasing the infectivity-reducing tag. The resulting phages were first tested with the infectivity-destroying detergent protease subtilisin; this resulted in a highly specific substrate at a 200-fold enrichment. In a second example, the protease ompT was used and led to an enrichment of the known double-arginine motif. The IMOP system thus substantially improves and simplifies previous systems.

Substrate Profiling of Cysteine Proteases Using a Combinatorial Peptide Library Identifies Functionally Unique Specificities

The substrate specificities of papain-like cysteine proteases (clan CA, family C1) papain, bromelain, and human cathepsins L, V, K, S, F, B, and five proteases of parasitic origin were studied using a completely diversified positional scanning synthetic combinatorial library. A bifunctional coumarin fluorophore was used that facilitated synthesis of the library and individual peptide substrates. The library has a total of 160,000 tetrapeptide substrate sequences completely randomizing each of the P1, P2, P3, and P4 positions with 20 amino acids. A microtiter plate assay format permitted a rapid determination of the specificity profile of each enzyme. Individual peptide substrates were then synthesized and tested for a quantitative determination of the specificity of the human cathepsins. Despite the conserved three-dimensional structure and similar substrate specificity of the enzymes studied, distinct amino acid preferences that differentiate each enzyme were identified. The specificities of cathepsins K and S partially match the cleavage site sequences in their physiological substrates. Capitalizing on its unique preference for proline and glycine at the P2 and P3 positions, respectively, selective substrates and a substrate-based inhibitor were developed for cathepsin K. A cluster analysis of the proteases based on the complete specificity profile provided a functional characterization distinct from standard sequence analysis. This approach provides useful information for developing selective chemical probes to study protease-related pathologies and physiologies.

Rapid peptide‐based screening on the substrate specificity of severe acute respiratory syndrome (SARS) coronavirus 3C‐like protease by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Severe acute respiratory syndrome coronavirus (SARS-CoV) 3C-like protease (3CLpro) mediates extensive proteolytic processing of replicase polyproteins, and is considered a promising target for anti-SARS drug development. Here we present a rapid and high-throughput screening method to study the substrate specificity of SARS-CoV 3CLpro. Six target amino acid positions flanking the SARS-CoV 3CLpro cleavage site were investigated. Each batch of mixed peptide substrates with defined amino acid substitutions at the target amino acid position was synthesized via the “cartridge replacement” approach and was subjected to enzymatic cleavage by recombinant SARS-CoV 3CLpro. Susceptibility of each peptide substrate to SARS-CoV 3CLpro cleavage was monitored simultaneously by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The hydrophobic pocket in the P2 position at the protease cleavage site is crucial to SARS-CoV 3CLpro-specific binding, which is limited to substitution by hydrophobic residue. The binding interface of SARS-CoV 3CLpro that is facing the P1′ position is suggested to be occupied by acidic amino acids, thus the P1′ position is intolerant to acidic residue substitution, owing to electrostatic repulsion. Steric hindrance caused by some bulky or β-branching amino acids in P3 and P2′ positions may also hinder the binding of SARS-CoV 3CLpro. This study generates a comprehensive overview of SARS-CoV 3CLpro substrate specificity, which serves as the design basis of synthetic peptide-based SARS-CoV 3CLpro inhibitors. Our experimental approach is believed to be widely applicable for investigating the substrate specificity of other proteases in a rapid and high-throughput manner that is compatible for future automated analysis.