Dai Luyuan

Cloning and expression of a luxRhomologue from Xanthomonas oryzae pv. oryzae

LuxR homologues are the main components of LuxR/LuxI circuit in Quorum Sensing (QS) of Gram-negative bacteria. A luxR homologue, designated as xooR, was cloned from X. oryzae pv. oryzae. The xooR gene is a transcription factor with 765 bp in length, and encodes a 254-amino acid putative protein with a molecular weight and an isoelectric point of 28.3 ku and 8.72 respectively. Amino acids 15 to 171 from the N-terminus are the Autoin-bind domain of XooR whereas amino acids 191 to 245 form a helix-turn-helix (HTH) motif that serves as the DNA-binding domain. In this study, XooR was expressed as a fusion protein along with green fluorescent protein (GFP), using pET-24a-d (+), a prokaryotic expression vector. Western blot showed that the xooR gene was successfully expressed in vitro in E.coli as a XooR-GFP fusion protein with a size of 54 ku.