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  • Pma1 is an alkali/alkaline earth metal cation ATPase that preferentially transports Na(+) and K(+) across the Mycobacterium smegmatis plasma membrane.

Pma1 is an alkali/alkaline earth metal cation ATPase that preferentially transports Na(+) and K(+) across the Mycobacterium smegmatis plasma membrane.

Microbiological research (2015-06-14)
Carlos Ayala-Torres, Lorena Novoa-Aponte, Carlos Y Soto
ABSTRACT

Mycobacterium smegmatis Pma1 is the orthologue of M. tuberculosis P-type ATPase cation transporter CtpF, which is activated under stress conditions, such as hypoxia, starvation and response to antituberculous and toxic substances. The function of Pma1 in the mycobacterial processes across the plasma membrane has not been characterised. In this work, bioinformatic analyses revealed that Pma1 likely contains potential sites for, Na(+), K(+) and Ca(2+) binding and transport. Accordingly, RT-qPCR experiments showed that M. smegmatis pma1 transcription is stimulated by sub-lethal doses of Na(+), K(+) and Ca(2+); in addition, the ATPase activity of plasma membrane vesicles in recombinant Pma1-expressing M. smegmatis cells is stimulated by treatment with these cations. In contrast, M. smegmatis cells homologously expressing Pma1 displayed tolerance to high doses of Na(+) and K(+) but not to Ca(2+) ions. Consistently, the recombinant protein Km embedded in plasma membrane demonstrated that Ca(2+) has more affinity for Pma1 than Na(+) and K(+) ions; furthermore, the estimation of Vmax/Km suggests that Na(+) and K(+) ions are more efficiently translocated than Ca(2+). Thus, these results strongly suggest that Pma1 is a promiscuous alkali/alkaline earth cation ATPase that preferentially transports Na(+) and/or K(+) across the mycobacterial plasma membrane.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Bismuth(III) citrate, 99.99% trace metals basis, −325 mesh
Sigma-Aldrich
Citrate Concentrated Solution, BioUltra, for molecular biology, 1 M in H2O
Sigma-Aldrich
Citrate Concentrated Solution, BioReagent, suitable for coagulation assays, 4 % (w/v)