Solution structure of ApaG from Xanthomonas axonopodis pv. citri reveals a fibronectin-3 fold

Daniel O. Cicero, Gian M. Contessa, Thelma A. Pertinhez, Mariana Gallo, Angela M. Katsuyama, Maurizio Paci, Chuck S. Farah, Alberto Spisni

Research output: Contribution to journalArticlepeer-review


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 Xanthomonus axonopodis pv. citri (ApaGXac) with the aim to shed some light on its molecular function. ApaGXac 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 ApaGXac does not bind ATP or GTP, in vitro. On the other hand, ApaGXac 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.

Original languageEnglish
Pages (from-to)490-500
Number of pages11
JournalProteins: Structure, Function and Genetics
Issue number2
Publication statusPublished - May 1 2007


  • ApaG
  • Fibronectin type III motif
  • Immunoglobulin fold
  • NMR
  • Protein structure
  • Xanthomonas axonopodis pv. citri

ASJC Scopus subject areas

  • Genetics
  • Structural Biology
  • Biochemistry


Dive into the research topics of 'Solution structure of ApaG from Xanthomonas axonopodis pv. citri reveals a fibronectin-3 fold'. Together they form a unique fingerprint.

Cite this