(渤海大学 食品科学与工程学院/生鲜农产品贮藏加工及安全控制技术 国家地方联合工程研究中心, 辽宁 锦州 121013)
(College of Food Science and Engineering/National & Local Joint Engineering Research Center of Storage, Processing and Safety Control Technology for Fresh Agricultural and Aquatic Products, Bohai University, Jinzhou 121013, China)
Outer membrane lipoprotein receptor LolB is a key factor for gram-negative bacteria to transport lipoprotein. Bioinformatics methods and real-time fluorescence quantitative PCR were used to investigate the physicochemical properties, structure and function of LolB in Shewanella putrefaciens from aquatic products and its gene expression changes under different environment. The results showed that lolB gene had high sequence conservation property and LolB was a stable hydrophilic protein with a molecular weight of about 23ku. LolB contained signal peptides and 21 phosphorylation sites, but had no transmembrane structure. The secondary structure of LolB was mainly random coil and β -folding, and the tertiary structure was β barrel-shaped. LolB was predicted to interact with a variety of proteins, including LolA of lipoprotein transport system, LolC and LolE family transmembrane proteins, ABC transport-related proteins, catalytic cracking glycotransferase involved in increasing cell membrane rigidity and maintaining cytoplasmic stability. Fluorescence quantitative PCR results showed that the expression of lolB gene was up-regulated when the bacteria were subjected to a certain degree of stravation, ethanol, osmotic pressure and high temperature stress, which presented a trend of up-regulation and then down-regulation with the increase of stress degree. At 4℃, lolB gene expression pattern was similar to that of the control group. Exogenous signal molecules C6-HSL induced high expression of lolB and could interact with Leu51 residue of LolB protein through π-alkyls. It was hoped that the results could provided a preliminary analysis of the function of LolB in S. putrefaciens and offered a new idea for the targeted inhibition of S. putrefaciens in aquatic products.