The short C-terminal hydrophilic domain of NhaH Na+/H+ antiporter from Halobacillus dabanensis with roles in resistance to salt and in pH sensing

• 来源期刊: 科学通报（英文版）
• 年，卷（期）: 2008,（21）
• 页码范围: 3311-3316
• 页数: 6页
• 语种: 英文
• DOI: 10.1007/s 11434-008-0431-1

摘要

The Na+/H+ antiporter plays key roles in maintaining low cytoplasmic Na+ level and pH homeostasis,while little is known about the Carboxyl-terminal hydrophilic tails of prokaryotic antiporters. In our previous study, the first Na+/H+ antiporter gene nhaH from moderate halophiles was cloned from Halo-bacillus dabanensis D-8 by functional complementation. A topological model suggested that only nine amino acid residues (395PLIKKLGMI403) existed in the hydrophilic C-terminal domain of NhaH. The C-terminal truncated mutant of NhaH was constructed by PCR strategy and designated as nhaH△C. Salt tolerance experiment demonstrated that the deletion of hydrophilic C-terminal nine amino acid resi-dues significantly inhibited the complementation ability of E. coli KNabc, in which three main Na+/H+ antiporters nhaA, nhaB and chaA were deleted. Everted membrane vesicles prepared from E. coli KNabc/nhaHAC decreased both Na+/H+ and Li+/H+ exchange activities of NhaH, and also resulted in an acidic shift of its pH profile for Na+, indicating a critical role of the short C-terminal domain of NhaH antiporter in alkali cation binding/translocation and pH sensing.