A novel NhaD-type Na^sup +^/H^sup +^ antiporter from the moderate halophile and alkaliphile Halomonas alkaliphila

• Published in: Canadian journal of microbiology Vol. 63; no. 7; p. 596
• Main Authors: Wang, Yanhong, Song, Na, Yang, Lina, Abdel-motaal, Heba, Zhang, Rui, Zhang, Zhenglai, Meng, Fankui, Jiang, Juquan
• Format: Journal Article
• Language: English
• Published: Ottawa Canadian Science Publishing NRC Research Press 01.07.2017
• Subjects: Amino acid sequence; Antiport; Deoxyribonucleic acid; DNA; E coli; Escherichia coli; Genomics; Hydrogen; Lithium chloride; Membrane vesicles; Microbiology; Na+/H+-exchanging ATPase; Nucleotide sequence; pH effects; Phylogenetics; Phylogeny; Sodium chloride; Studies
• ISSN: 0008-4166

In this study, a NhaD-type Na+/H+ antiporter gene designated Ha-nhaD was obtained by selection of genomic DNA from the moderate halophile and alkaliphile Halomonas alkaliphila in Escherichia coli KNabc lacking 3 major Na+/H+ antiporters. The presence of Ha-NhaD conferred tolerance of E. coli KNabc to NaCl up to 0.6 mol-L^sup -1^ and to LiCl up to 0.2 mol-L^sup -1^ and to an alkaline pH. pH-dependent Na+(Li+)/H+ antiport activity was detected from everted membrane vesicles prepared from E. coli KNabc/pUC-nhaD but not those of KNabc/pUC18. Ha-NhaD exhibited Na+(Li+)/H+ antiport activity over a wide pH range from 7.0 to 9.5, with the highest activity at pH 9.0. Protein sequence alignment and phylogenetic analysis revealed that Ha-NhaD is significantly different from the 7 known NhaD-type Na+/H+ antiporters, including Dw-NhaD, Dl-NhaD, Vp-NhaD, Vc-NhaD, Aa-NhaD, He-NhaD, and Ha-NhaD1. Although Ha-NhaD showed a closer phylogenetic relationship with Ha-NhaD2, a significant difference in pH-dependent activity profile exists between Ha-NhaD and Ha-NhaD2. Taken together, Ha-nhaD encodes a novel pH-dependent NhaD-type Na+/H+ antiporter.