Open AccessPutative paired small multidrug resistance family proteins PsmrAB , the homolog of Y vd SR , actually function as a novel two‐component N a + / H + antiporter
Author(s) -
Jiang Juquan,
Wang Lei,
Zhang Hua,
Wu Haiping,
Huang Haipeng,
Yang Lifu
Publication year - 2013
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/1574-6968.12008
Subject(s) - antiporter , antiporters , escherichia coli , biology , ethidium bromide , sodium–hydrogen antiporter , gene , biochemistry , microbiology and biotechnology , chemistry , dna , sodium , membrane , organic chemistry
In this study, metagenomic DNA was screened for the N a + / H + antiporter gene from the halophilic bacteria from D aban S alt L ake using E scherichia coli KN abc lacking three major N a + / H + antiporters, and two genes psmrAB predicted to encode paired small multidrug resistance ( PSMR ) family proteins, the homolog of Y vd SR , were finally cloned. Only the simultaneous presence of psmrAB , but not the single gene alone, conferred the tolerance of E . coli KN abc to up to 0.6 M N a C l and at alkaline pH . p H ‐dependent N a + ( L i + )/ H + antiport activity was detected from everted membrane vesicles prepared from E . coli KN abc cells carrying psmrAB , which had the highest activity at p H 9.0. However, a detailed test for antimicrobial drugs showed that E . coli DH 5α with psmrAB only exhibited slight resistance to chloramphenicol, but not other representative antimicrobial drugs especially ethidium bromide. Protein sequence alignment showed that neither PsmrA nor PsmrB has homology with known single‐gene or multiple‐gene N a + / H + antiporters, or such proteins as TetA(L) and MdfA with N a + / H + antiport activity. Taken together, PsmrAB should function mainly as a novel two‐component N a + / H + antiporter. This is the first example of a PSMR family member that exhibits N a + / H + antiporter activity.