SEQUENCE AND STRUCTURE COMPARISON SUGGEST THAT METHIONINE AMINOPEPTIDASE, PROLIDASE, AMINOPEPTIDASE-P, AND CREATINASE SHARE A COMMON FOLD

Amino acid sequence comparison suggests that the structure of Escherichia coli methionine aminopeptidase (EC 3.4.11.18) and the C-terminal domain of Pseudomonas putida creatinase (EC 3.5.3.3) are related. A detailed comparison of the three-dimensional folds of the two enzymes confirms this homology: within an almost-equal-to 260-residue chain segment, 218 C(alpha) atoms of the structures superimpose within 2.5 angstrom; only 41 of these overlapping positions (i.e., 19%) feature identical amino acids in the two protein chains. Notwithstanding this striking correspondence in structure, methionine aminopeptidase binds and is stimulated by Co2+, while creatinase is not a metal-dependent enzyme. Searches of protein data banks using sequence and structure-based profiles reveal other enzymes, including aminopeptidase P (EC 3.4.11.9), prolidase (EC 3.4.13.9), and agropine synthase, that likely share the same ''pita-bread'' fold common to creatinase and methionine aminopeptidase.