title: Cloning and identification of Group 1 mrp operon encoding a novel monovalent cation/proton antiporter system from the moderate halophile Halomonas zhaodongensis.
abstract: The novel species Halomonas zhaodongensis NEAU-ST10-25(T) recently identified by our group is a moderate halophile which can grow at the range of 0-2.5 M NaCl (optimum 0.5 M) and pH 6-12 (optimum pH 9). To explore its halo-alkaline tolerant mechanism, genomic DNA was screened from NEAU-ST10-25(T) in this study for Na(+)(Li(+))/H(+) antiporter genes by selection in Escherichia coli KNabc lacking three major Na(+)(Li(+))/H(+) antiporters. One mrp operon could confer tolerance of E. coli KNabc to 0.8 M NaCl and 100 mM LiCl, and an alkaline pH. This operon was previously mainly designated mrp (also mnh, pha or sha) due to its multiple resistance and pH-related activity. Here, we will also use mrp to designate the homolog from H. zhaodongensis (Hz_mrp). Sequence analysis and protein alignment showed that Hz_mrp should belong to Group 1 mrp operons. Further phylogenetic analysis reveals that Hz_Mrp system should represent a novel sub-class of Group 1 Mrp systems. This was confirmed by a significant difference in pH-dependent activity profile or the specificity and affinity for the transported monovalent cations between Hz_Mrp system and all the known Mrp systems. Therefore, we propose that Hz_Mrp should be categorized as a novel Group 1 Mrp system.
authors.affiliation: Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, 150030, People's Republic of China.
authors.forename: Lin
authors.initials: L
authors.lastname: Meng
authors.forename: Shan
authors.initials: S
authors.lastname: Hong
authors.forename: Henan
authors.initials: H
authors.lastname: Liu
authors.forename: Haipeng
authors.initials: H
authors.lastname: Huang
authors.forename: Hao
authors.initials: H
authors.lastname: Sun
authors.forename: Tong
authors.initials: T
authors.lastname: Xu
authors.forename: Juquan
authors.initials: J
authors.lastname: Jiang
mesh_terms: D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D020632:Halomonas / Q000235:genetics / Q000378:metabolism*; D017136:Ion Transport; D007700:Kinetics; D008094:Lithium / Q000378:metabolism*; D009876:Operon; D010802:Phylogeny; D011522:Protons; D055049:Salt Tolerance; D012964:Sodium / Q000378:metabolism*
chemical_list: D017920:Antiporters; D001426:Bacterial Proteins; D011522:Protons; D008094:Lithium; D012964:Sodium