Characterization of a P-type Na+-ATPase of a facultatively anaerobic alkaliphile, Exiguobacterium aurantiacum.
A facultatively anaerobic alkaliphile, Exiguobacterium aurantiacum, possesses a P-type Na(+)-stimulated ATPase in the membrane (Koyama, N. (1999) Curr. Microbiol. 39, 27-30). In this study, we attempted to purify and characterize the enzyme. The ATPase appears to consist of a single polypeptide with an apparent molecular mass of 100 kDa. The enzyme exhibited an optimum pH for activity at around 9. The enzyme was strongly inhibited by vanadate (50% inhibition observed at 3 microm) and forms an acylphosphate intermediate, suggesting a P-type ATPase. The enzyme, when reconstituted into soybean phospholipid vesicles, exhibited ATP-dependent (22)Na(+) uptake, which was completely inhibited by gramicidin. The reconstituted vesicles exhibited a generation of membrane potential (positive, inside). The enzyme is likely to be involved in an electrogenic transport of Na(+).
Ueno
S
S
Department of Chemistry, Faculty of Science, Chiba University, Yayoi, Inage-ku, Chiba 263-8522, Japan.
Kaieda
N
N
Koyama
N
N
D000251:Adenosine Triphosphatases / Q000302:isolation & purification / Q000378:metabolism*; D001421:Bacteria, Anaerobic / Q000201:enzymology*; D027682:Cation Transport Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D008564:Membrane Potentials; D010766:Phosphorylation; D029701:Saccharomyces cerevisiae Proteins; D000254:Sodium-Potassium-Exchanging ATPase
D027682:Cation Transport Proteins; C086375:ENA1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase