Format

Send to

Choose Destination
J Biol Chem. 2016 Dec 9;291(50):26056-26065. Epub 2016 Oct 24.

Alkaline Response of a Halotolerant Alkaliphilic Halomonas Strain and Functional Diversity of Its Na+(K+)/H+ Antiporters.

Author information

1
From the State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100 and.
2
the State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
3
From the State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100 and ycy21th@sdu.edu.cn.

Abstract

Halomonas sp. Y2 is a halotolerant alkaliphilic strain from Na+-rich pulp mill wastewater with high alkalinity (pH >11.0). Transcriptome analysis of this isolate revealed this strain may use various transport systems for pH homeostasis. In particular, the genes encoding four putative Na+/H+ antiporters were differentially expressed upon acidic or alkaline conditions. Further evidence, from heterologous expression and mutant studies, suggested that Halomonas sp. Y2 employs its Na+/H+ antiporters in a labor division way to deal with saline and alkaline environments. Ha-NhaD2 displayed robust Na+(Li+) resistance and high transport activities in Escherichia coli; a ΔHa-nhaD2 mutant exhibited growth inhibition at high Na+(Li+) concentrations at pH values of 6.2, 8.0, and 10.0, suggesting its physiological role in osmotic homeostasis. In contrast, Ha-NhaD1 showed much weaker activities in ion exporting and pH homeostasis. Ha-Mrp displayed a combination of properties similar to those of Mrp transporters from some Bacillus alkaliphiles and neutrophiles. This conferred obvious Na+(Li+, K+) resistance in E. coli-deficient strains, as those ion transport spectra of some neutrophil Mrp antiporters. Conversely, similar to the Bacillus alkaliphiles, Ha-Mrp showed central roles in the pH homeostasis of Halomonas sp. Y2. An Ha-mrp-disrupted mutant was seriously inhibited by high concentrations of Na+(Li+, K+) but only under alkaline conditions. Ha-NhaP was determined to be a K+/H+ antiporter and shown to confer strong K+ resistance both at acidic and alkaline stresses.

KEYWORDS:

membrane protein; pH regulation; potassium transport; sodium-proton exchange; stress response; transcriptomics

PMID:
27777302
PMCID:
PMC5207076
DOI:
10.1074/jbc.M116.751016
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center