This domain is found in Xaa-Pro dipeptidase from Escherichia coli (PepQ), a metalloprotease that catalyse the cleavage of Xaa-Pro dipeptides. This protein is organised into N-terminal (this entry) and C-terminal (usually Pfam:PF00557) domains and adopts a dimeric configuration. This domain shows an alpha-beta structure with four helices, one pair flanking each side of the six-stranded mixed beta-sheet [1-5].

1: Structural insights into the dual activities of the nerve agent degrading organophosphate anhydrolase/prolidase. Vyas NK, Nickitenko A, Rastogi VK, Shah SS, Quiocho FA; Biochemistry. 2010;49:547-559. PMID:20000741

2: Organophosphorus acid anhydrolase from Alteromonas macleodii: structural study and functional relationship to prolidases. Stepankova A, Duskova J, Skalova T, Hasek J, Koval' T, Ostergaard LH, Dohnalek J; Acta Crystallogr Sect F Struct Biol Cryst Commun. 2013;69:346-354. PMID:23545636

3: Structural basis of substrate selectivity of E. coli prolidase. Weaver J, Watts T, Li P, Rye HS; PLoS One. 2014;9:e111531. PMID:25354344

4: Engineering the Organophosphorus Acid Anhydrolase Enzyme for Increased Catalytic Efficiency and Broadened Stereospecificity on Russian VX. Daczkowski CM, Pegan SD, Harvey SP; Biochemistry. 2015;54:6423-6433. PMID:26418828

5: Repurposing a bacterial prolidase for organophosphorus hydrolysis: Reshaped catalytic cavity switches substrate selectivity. Yang J, Xiao YZ, Li R, Liu Y, Long LJ; Biotechnol Bioeng. 2020;117:2694-2702. PMID:32515491