5ntb
From Proteopedia
Streptomyces papain inhibitor (SPI)
Structural highlights
Function[PAPI_STRMB] Stress protein produced under hyperthermal stress conditions. Serves as a glutamine and lysine donor substrate for transglutaminase. Inhibits the cysteine proteases papain and bromelain as well as the bovine serine protease trypsin. Has hardly any or no effect on subtilisin, bovine chymotrypsin, proteinase K from T.album, transglutaminase-activating metalloproteinase (TAMEP) from S.mobaraensis, dispase from B.polymyxa, thermolysin from B.thermoproteolyticus or collagenase from C.histolyticum.[1] Publication Abstract from PubMedTransglutaminase from Streptomyces mobaraensis (MTG) has become a powerful tool to covalently and highly specifically link functional amines to glutamine donor sites of therapeutic proteins. However, details regarding the mechanism of substrate recognition and interaction of the enzyme with proteinaceous substrates still remain mostly elusive. We have determined the crystal structure of the Streptomyces papain inhibitory protein (SPIp ), a substrate of MTG, to study the influence of various substrate amino acids on positioning glutamine to the active site of MTG. SPIp exhibits a rigid, thermo-resistant double-psi-beta-barrel fold that is stabilized by two cysteine bridges. Incorporation of biotin cadaverine identified Gln-6 as the only amine acceptor site on SPIp accessible for MTG. Substitution of Lys-7 demonstrated that small and hydrophobic residues in close proximity to Gln-6 favour MTG-mediated modification and are likely to facilitate introduction of the substrate into the front vestibule of MTG. Moreover, exchange of various surface residues of SPIp for arginine and glutamate/aspartate outside the glutamine donor region influences the efficiency of modification by MTG. These results suggest the occurrence of charged contact areas between MTG and the acyl donor substrates beyond the front vestibule, and pave the way for protein engineering approaches to improve the properties of artificial MTG-substrates used in biomedical applications. This article is protected by copyright. All rights reserved. Illuminating structure and acyl donor sites of a physiological transglutaminase substrate from Streptomyces mobaraensis.,Juettner NE, Schmelz S, Bogen JP, Happel D, Fessner WD, Pfeifer F, Fuchsbauer HL, Scrima A Protein Sci. 2018 Feb 12. doi: 10.1002/pro.3388. PMID:29430769[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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