title: Expression of the Na+/H+ antiporter gene (g1-nhaC) of alkaliphilic Bacillus sp. G1 in Escherichia coli.
abstract: A Na(+)/H(+) antiporter gene was isolated from alkaliphilic Bacillus sp. G1. The full-length sequence of the Na(+)/H(+) antiporter gene was obtained using a genome walking method, and designated as g1-nhaC. An ORF preceded by a promoter-like sequence and a Shine-Dalgarno sequence, and followed by a terminator-like sequence was identified. The deduced amino acid sequence consists of 535 amino acids, and a calculated molecular mass of 57 776 Da. g1-nhaC was subsequently cloned into pET22b(+) and expressed in Escherichia coli BL21 (DE3). Recombinant E. coli harboring the g1-nhaC gene was able to grow in modified L medium at various concentrations of NaCl (0.2-2.0 M) at different pH values. The recombinant bacteria grew well in the medium with concentrations of NaCl as high as 1.75 M at pH 8.0-9.0. Minimal growth was observed at 2.0 M NaCl, pH 8.0-9.0. At pH 10, the recombinant bacteria grew well in a medium with a low concentration of NaCl (0.2 M). These results suggested that the g1-NhaC antiporter from Bacillus sp. G1 plays a role in Na(+) extrusion at lower pH values and in pH homeostasis at pH 10 under Na(+)-limiting conditions.
authors.affiliation: Department of Bioprocess Engineering, Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia.
authors.forename: Chong Wai
authors.initials: CW
authors.lastname: Liew
authors.forename: Rosli Md
authors.initials: RM
authors.lastname: Illias
authors.forename: Nor Muhammad
authors.initials: NM
authors.lastname: Mahadi
authors.forename: Nazalan
authors.initials: N
authors.lastname: Najimudin
mesh_terms: D000595:Amino Acid Sequence; D001407:Bacillus / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003001:Cloning, Molecular; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology*; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016366:Open Reading Frames; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D013728:Terminator Regions, Genetic
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004269:DNA, Bacterial; D017923:Sodium-Hydrogen Exchangers; D012965:Sodium Chloride