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Solution structure of ApaG from Xanthomonas axonopodis pv. citri reveals a fibronectin‐3 fold
Author(s) -
Cicero Daniel O.,
Contessa Gian M.,
Pertinhez Thelma A.,
Gallo Mariana,
Katsuyama Angela M.,
Paci Maurizio,
Farah Chuck S.,
Spisni Alberto
Publication year - 2007
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.21277
Subject(s) - antiparallel (mathematics) , xanthomonas , biology , hypothetical protein , homology (biology) , structural motif , genetics , computational biology , biochemistry , bacteria , amino acid , gene , physics , quantum mechanics , magnetic field
ApaG proteins are found in a wide variety of bacterial genomes but their function is as yet unknown. Some eukaryotic proteins involved in protein‐protein interactions, such as the human polymerase δ‐interacting protein (PDIP38) and the F Box A (FBA) proteins, contain ApaG homology domains. We have used NMR to determine the solution structure of ApaG protein from the plant pathogen Xanthomonas axonopodis pv. citri (ApaG Xac ) with the aim to shed some light on its molecular function. ApaG Xac is characterized by seven antiparallel β strands forming two β sheets, one containing three strands (ABE) and the other four strands (GFCC′). Relaxation measurements indicate that the protein has a quite rigid structure. In spite of the presence of a putative GXGXXG pyrophosphate binding motif ApaG Xac does not bind ATP or GTP, in vitro . On the other hand, ApaG Xac adopts a fibronectin type III (Fn3) fold, which is consistent with the hypothesis that it is involved in mediating protein‐protein interactions. The fact that the proteins of ApaG family do not display significant sequence similarity with the Fn3 domains found in other eukaryotic or bacterial proteins suggests that Fn3 domain may have arisen earlier in evolution than previously estimated. Proteins 2007 © 2007 Wiley‐Liss, Inc.