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

作　　者：YANG LiFu ZHANG Bo WANG Lei YANG SuSheng 

机构地区：[1]1Department of Microbiology and Immunology, College of Biological Sciences, and Key Laboratory of Agro-Microbial Resource and Application, Ministry of Agriculture, China Agricultural University, Beijing 100193, China [2]Rubber Research Institute, and Key Laboratory of Physiology for Tropical Crops, Ministry of Agriculture, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan 571737, China

出　　处：《Chinese Science Bulletin》2008年第21期3311-3316,共6页

基　　金：the National High Technology Research and Development Program of China (Grant No. 2003AA241150);International Cooperation Program for Science and Technology (Grant No.2006DFA31060)

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/nhaH△C 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.The Na^＋/H^＋ antiporter plays key roles in maintaining low cytoplasmic NaNa^＋ 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 Halobacillus 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 residues significantly inhibited the complementation ability of E. coil KNabc, in which three main Na^＋/H^＋ antiporters nhaA, nhaB and chaA were deleted. Everted membrane vesicles prepared from E. coil 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.

关 键 词：反向转运 亲水性 基因表达 生物学 

分 类 号：Q78[生物学—分子生物学]