title: Insight into the substrate length restriction of M32 carboxypeptidases: characterization of two distinct subfamilies.
abstract: 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.
authors: The Ohio State Biophysics Program, The Ohio State University, 484 West 12th Avenue, Columbus, Ohio 43210, USA.
authors: Marianne M
authors: MM
authors: Lee
authors: Clara E
authors: CE
authors: Isaza
authors: James D
authors: JD
authors: White
authors: Rita P-Y
authors: RP
authors: Chen
authors: George F-C
authors: GF
authors: Liang
authors: Hannah T-F
authors: HT
authors: He
authors: Sunney I
authors: SI
authors: Chan
authors: Michael K
authors: MK
authors: Chan
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D001120:Arginine / Q000737:chemistry; D001412:Bacillus subtilis / Q000378:metabolism; D002268:Carboxypeptidases / Q000737:chemistry*; D020134:Catalytic Domain; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry; D007700:Kinetics; D045726:Metalloproteases / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016963:Thermus thermophilus / Q000378:metabolism
chemical_list: D000596:Amino Acids; D004247:DNA; D001120:Arginine; D002268:Carboxypeptidases; D045726:Metalloproteases