title: Function of MsiR on canavanine-mediated repression in Mesorhizobium tianshanense.
abstract: Mesorhizobium tianshanense employs MsiA as canavanine exporter, which is upregulated by MsiR, to successfully form a symbiosis with the legume Glycyrrhiza uralensis. In this research, through gel-shift and bacterial two-hybrid examination, MsiR was found to spontaneously form dimers and bind to msiA promoter without additional canavanine. Six truncated forms of MsiR were constructed, and the conserved helix-turn-helix (HTH), substrate-binding, and surface-loop domains were found essential for MsiR functions. Random mutagenesis was used to study the functional sites of MsiR. Seven point mutants were selected, in which three mutants constitutively induced msiA expression without additional canavanine, two mutants partially changed substrate specificity, and the other two were almost null mutants. Results from the site mutation show that the functional subunits (HTH domain, dimerization interface domains, and C-terminal) are important in the conformation and induction ability of MsiR.
authors: Department of Microbiology, MOA Key Lab of Microbiological Engineering of Agricultural Environment, Nanjing Agricultural University, Nanjing, China, mol_microb@njau.edu.cn.
authors: Zengtao
authors: Z
authors: Zhong
authors: Yuning
authors: Y
authors: Wang
authors: Wu
authors: W
authors: Ping
authors: Jun
authors: J
authors: Ling
authors: Huiming
authors: H
authors: Zheng
authors: Hui
authors: H
authors: Wang
authors: Jun
authors: J
authors: Zhu
mesh_terms: D001692:Biological Transport / Q000235:genetics / Q000502:physiology*; D002172:Canavanine / Q000378:metabolism*; D029882:Glycyrrhiza uralensis / Q000382:microbiology*; D059128:Mesorhizobium / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D011487:Protein Conformation; D013559:Symbiosis / Q000235:genetics; D015533:Transcriptional Activation
chemical_list: D002172:Canavanine