6r55
Crystal structure of PPEP-1(E184K)
Structural highlights
FunctionPPEP1_CLOD6 Zinc-dependent endoprotease with a unique preference for proline residues surrounding the scissile bond. Exhibits a high preference for an asparagine at the P2 position and hydrophobic residues (Val, Ile, Leu) at the P3 position. Efficiently cleaves the LPXTG cell surface proteins CD630_28310 and CD630_32460 at multiple cleavage sites in vivo. Has a role in the regulation of C.difficile adhesion versus motility by cleaving surface adhesion proteins such as the collagen binding protein CD630_28310, and is important for efficient infection. Is also able to cleave fibronectin and fibrinogen in vitro; cleaves at the N-terminus of the beta-chain of fibrinogen. Destabilizes the fibronectin network produced by human fibroblasts. Therefore, may be important in key steps of clostridial pathogenesis by degrading extracellular matrix components associated with the gut epithelial cells. To a lesser extent, IgA1, IgA2, and human HSP 90-beta, but not HSP 90-alpha, are also substrates for the enzyme. Is not active on different collagen types, casein and gelatin.[1] [2] [3] [4] Publication Abstract from PubMedPro-Pro endopeptidase-1 (PPEP-1) is a secreted metalloprotease from the bacterial pathogen Clostridium difficile that cleaves two endogenous adhesion proteins. PPEP-1 is therefore important for bacterial motility and hence for efficient gut colonization during infection. PPEP-1 exhibits a unique specificity for Pro-Pro peptide bonds within the consensus sequence VNP downward arrowPVP. In this study, we combined information from crystal and NMR structures with mutagenesis and enzyme kinetics to investigate the mechanism and substrate specificity of PPEP-1. Our analyses revealed that the substrate-binding cleft of PPEP-1 is shaped complementary to the major conformation of the substrate in solution. We found that it possesses features that accept a tertiary amide and help discriminate P1' residues by their amide hydrogen bond-donating potential. We also noted that residues Lys-101, Trp-103, and Glu-184 are crucial for proteolytic activity. Upon substrate binding, these residues position a flexible loop over the substrate-binding cleft and modulate the second coordination sphere of the catalytic zinc ion. On the basis of these findings, we propose an induced-fit model in which pre-structured substrates are recognized, followed by substrate positioning within the active-site cleft and a concomitant increase in the Lewis acidity of the catalytic Zn2+ ion. In conclusion, our findings provide detailed structural and mechanistic insights into the substrate recognition and specificity of PPEP-1 from the common gut pathogen Clostridium difficile. Molecular determinants of the mechanism and substrate specificity of Clostridium difficile proline-proline endopeptidase-1.,Pichlo C, Juetten L, Wojtalla F, Schacherl M, Diaz D, Baumann U J Biol Chem. 2019 Jun 10. pii: RA119.009029. doi: 10.1074/jbc.RA119.009029. PMID:31182482[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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