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

• Published in: Canadian journal of microbiology Vol. 63; no. 7; pp. 596 - 607
• 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: Canada NRC Research Press 01.07.2017
• Subjects: Alkalies; Amino Acid Sequence; antiport Na; antiporter; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Escherichia coli - genetics; Escherichia coli - physiology; Halomonas - genetics; Halomonas alkaliphila; halophile et alcaliphile modéré; Hydrogen-Ion Concentration; moderate halophile and alkaliphile; NhaD; pH-dependent activity profile; Phylogeny; profil d’activités dépendantes du pH; Salt-Tolerant Plants; Sodium Chloride - metabolism; Sodium-Hydrogen Exchangers - genetics; Sodium-Hydrogen Exchangers - metabolism; pH-dependent activity profile; profil d’activités dépendantes du pH; Na+/H+ antiporter; NhaD; Halomonas alkaliphila; antiport Na+/H; halophile et alcaliphile modéré; moderate halophile and alkaliphile
• ISSN: 0008-4166; 1480-3275
• DOI: 10.1139/cjm-2017-0104

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 –1 and to LiCl up to 0.2 mol·L –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.