title: Identification and characterization of the biochemical function of Agrobacterium T-complex-recruiting protein Atu5117.
abstract: Atu5117 from Agrobacterium tumefaciens is a highly conserved protein with a putative nucleotidyltransferase domain in its N-terminal region and a putative higher eukaryotes and prokaryotes nucleotide-binding domain in its C-terminal region. This protein has been shown to be a T-complex-recruiting protein that can recruit T-complex from the cytosol to the polar VirB/D4 type IV secretion system (T4SS). However, the biochemical function of Atu5117 is still unknown. Here, we show that Atu5117 is a (d)NTPase. Although no proteins with nucleotidyltransferase and higher eukaryotes and prokaryotes nucleotide-binding domains were identified as (d)NTPases, Atu5117 was able to convert all eight canonical NTPs and dNTPs to NDP, dNDP and inorganic phosphate in vitro, and required Mg(2+) for its (d)NTPase activity. The kinetic parameters of Atu5117 (d)NTPase for eight substrates were characterized. Kinetic data showed that Atu5117 (d)NTPase preferred ATP as its substrate. The optimal conditions for (d)NTPase activity of Atu5117 were very similar to those required for Agrobacterium tumorigenesis. The kinetic parameters of (d)NTPase of Atu5117 for all four canonical NTPs were in the same orders of magnitude as the kinetic parameters of the ATPases identified in some components of the VirB/D4 T4SS. These results suggest that Atu5117 might function as an energizer to recruit T-complex to the T4SS transport site.
authors.affiliation: College of Bioscience and Biotechnology, Yangzhou University, China.
authors.forename: Diankun
authors.initials: D
authors.lastname: Gao
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Bian
authors.forename: Minliang
authors.initials: M
authors.lastname: Guo
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins
keywords: (d)NTPase; Agrobacterium Atu5117; T-complex-recruiting protein; enzyme kinetics; nucleotide hydrolysis