5mrv
From Proteopedia
Crystal structure of human carboxypeptidase O in complex with NvCI
Structural highlights
Function[CBPO_HUMAN] Carboxypeptidase which preferentially cleaves C-terminal acidic residues from peptides and proteins. Can also cleave C-terminal hydrophobic amino acids, with a preference for small residues over large residues.[1] [MCPI_NERVS] Metallocarboxypeptidase inhibitor. Has an inhibitory effect on bovine CPA1 and CPB2, human CPA1, CPA2, CPA4, CPB1 and CPB2, and porcine CPB1. Does not inhibit D.melanogaster svr (carboxypeptidase D). Shows no activity against serine proteases subtilisin or bovine trypsin, cysteine protease papain, and aspartyl protease porcine pepsin.[2] [UniProtKB:P01075] Publication Abstract from PubMedHuman metallocarboxypeptidase O (hCPO) is a recently discovered digestive enzyme localized to the apical membrane of intestinal epithelial cells. Unlike pancreatic metallocarboxypeptidases, hCPO is glycosylated and produced as an active enzyme with distinctive substrate specificity toward C-terminal (C-t) acidic residues. Here we present the crystal structure of hCPO at 1.85-A resolution, both alone and in complex with a carboxypeptidase inhibitor (NvCI) from the marine snail Nerita versicolor The structure provides detailed information regarding determinants of enzyme specificity, in particular Arg275, placed at the bottom of the substrate-binding pocket. This residue, located at "canonical" position 255, where it is Ile in human pancreatic carboxypeptidases A1 (hCPA1) and A2 (hCPA2) and Asp in B (hCPB), plays a dominant role in determining the preference of hCPO for acidic C-t residues. Site-directed mutagenesis to Asp and Ala changes the specificity to C-t basic and hydrophobic residues, respectively. The single-site mutants thus faithfully mimic the enzymatic properties of CPB and CPA, respectively. hCPO also shows a preference for Glu over Asp, probably as a consequence of a tighter fitting of the Glu side chain in its S1' substrate-binding pocket. This unique preference of hCPO, together with hCPA1, hCPA2, and hCPB, completes the array of C-t cleavages enabling the digestion of the dietary proteins within the intestine. Finally, in addition to activity toward small synthetic substrates and peptides, hCPO can also trim C-t extensions of proteins, such as epidermal growth factor, suggesting a role in the maturation and degradation of growth factors and bioactive peptides. Crystal structure and mechanism of human carboxypeptidase O: Insights into its specific activity for acidic residues.,Garcia-Guerrero MC, Garcia-Pardo J, Berenguer E, Fernandez-Alvarez R, Barfi GB, Lyons PJ, Aviles FX, Huber R, Lorenzo J, Reverter D Proc Natl Acad Sci U S A. 2018 Apr 24;115(17):E3932-E3939. doi:, 10.1073/pnas.1803685115. Epub 2018 Apr 10. PMID:29636417[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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