A UPF0118 family protein with uncharacterized function from the moderate halophile Halobacillus andaensis represents a novel class of Na+(Li+)/H+ antiporter

Ping Dong,Mingxue Yan,Jin Chen,Na Song,Juquan Jiang,Heba Abdel-Motaal,Lidan Wang,Rui Zhang,Jincheng Li,Lina Yang,Huiwen Chen

doi:10.1038/srep45936

Abstract

In this study, genomic DNA was screened from Halobacillus andaensis NEAU-ST10-40T by selection in Escherichia coli KNabc lacking three major Na+/H+ antiporters. One gene designated upf0118 exhibiting Na+(Li+)/H+ antiport activity was finally cloned. Protein alignment showed that UPF0118 shares the highest identity of 81.5% with an unannotated gene encoding a protein with uncharacterized protein function belonging to UPF0118 family from H. kuroshimensis, but shares no identity with all known specific Na+(Li+)/H+ antiporter genes or genes with Na+(Li+)/H+ antiport activity. Growth test, western blot and Na+(Li+)/H+ antiport assay revealed that UPF0118 as a transmembrane protein exhibits pH-dependent Na+(Li+)/H+ antiport activity. Phylogenetic analysis indicated that UPF0118 clustered with all its homologs belonging to UPF0118 family at a wide range of 22–82% identities with the bootstrap value of 92%, which was significantly distant with all known specific single-gene Na+(Li+)/H+ antiporters and single-gene proteins with the Na+(Li+)/H+ antiport activity. Taken together, we propose that UPF0118 should represent a novel class of Na+(Li+)/H+ antiporter. To the best of our knowledge, this is the first report on the functional analysis of a protein with uncharacterized protein function as a representative of UPF0118 family containing the domain of unknown function, DUF20.

Highlights

IntroductionThe E. coli multidrug resistance (MDR) protein MdfA with a broad-specificity MDR phenotype[36] was characterized to exhibit Na+(K+)/H+ antiport activity[37]
C-terminus truncated ORF1 has the highest identity of 76.0% with a putative glycine betaine transporter from Salimicrobium jeotgali, ORF2 has the highest identity of 73.0% with a hypothetical protein belonging to YugN-like family from an uncharacterized Bacillaceae species, ORF3 has the highest identity of 81.5% with a protein belonging to UPF0118 family with uncharacterized protein function from H. kuroshimensis, and ORF4 has the highest identity of 63.0% with a putative N-acetyltransferase from Halobacillus sp
We showed a protein with uncharacterized function, UPF0118, from the moderate halophile NEAU-ST10-40T exhibits Na+(Li+)/H+ antiport activity, whose homologs have not been annotated in their genomes as yet

Summary

Introduction

The E. coli multidrug resistance (MDR) protein MdfA with a broad-specificity MDR phenotype[36] was characterized to exhibit Na+(K+)/H+ antiport activity[37]. Putative paired small multidrug resistance family proteins PsmrAB, the homolog of YvdSR, were characterized to function mainly as a novel two-component Na+/H+ antiporter[38]. Of several screened resultant clones, to our surprise, one gene designated upf0118 showed the highest identity of 81.5% with an unannotated gene encoding a protein with uncharacterized protein function belonging to UPF0118 family from H. kuroshimensis, but showed no identity with all known specific Na+(Li+)/H+ antiporter genes or genes with Na+(Li+)/H+ antiport activity. We reported the cloning and characterization of upf0118 and propose that this novel protein belonging to UPF0118 family should represents a novel class of Na+(Li+)/H+ antiporter

Methods

Results

Conclusion