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Insight into the substrate length restriction of M32 carboxypeptidases: Characterization of two distinct subfamilies
Author(s) -
Lee Marianne M.,
Isaza Clara E.,
White James D.,
Chen Rita P.Y.,
Liang George F.C.,
He Hannah T.F.,
Chan Sunney I.,
Chan Michael K.
Publication year - 2009
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.22478
Subject(s) - subfamily , carboxypeptidase , biology , bacillus subtilis , genetics , biochemistry , enzyme , bacteria , gene
M32 carboxypeptidases are a distinct family of HEXXH metalloproteases whose structures exhibit a narrow substrate groove that is blocked at one end. Structural alignments with other HEXXH metalloprotease‐peptide complexes suggested an orientation in which the substrate is directed towards the back of the groove. This led us to hypothesize, and subsequently confirm that the maximum substrate length for M32 carboxypeptidases is restricted. Structural and sequence analyses implicate a highly conserved Arg at the back of the groove as being critical for this length restriction. However, the Thermus thermophilus and Bacillus subtilis M32 members lack this conserved Arg. Herein, we present the biochemical and structural characterization of these two proteins. Our findings support the important role of the conserved Arg in maintaining the length restriction, and reveal a proline‐rich loop as an alternate blocking strategy. Based on our results, we propose that M32 carboxypeptidases from Bacilli belong to a separate subfamily. Proteins 2009. © 2009 Wiley‐Liss, Inc.