Purification and properties of the F1F0 ATPase of Ilyobacter tartaricus, a sodium ion pump.
The ATPase of Ilyobacter tartaricus was solubilized from the bacterial membranes and purified. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme revealed the usual subunit pattern of a bacterial F1F0 ATPase. The polypeptides with apparent molecular masses of 56, 52, 35, 16.5, and 6.5 kDa were identified as the alpha, beta, gamma, epsilon, and c subunits, respectively, by N-terminal protein sequencing and comparison with the sequences of the corresponding subunits from the Na(+)-translocating ATPase of Propionigenium modestum. Two overlapping sequences were obtained for the polypeptides moving with an apparent molecular mass of 22 kDa (tentatively assigned as b and delta subunits). No sequence could be determined for the putative a subunit (apparent molecular mass, 25 kDa). The c subunits formed a strong aggregate with the apparent molecular mass of 50 kDa which required treatment with trichloroacetic acid for dissociation. The ATPase was inhibited by dicyclohexyl carbodiimide, and Na+ ions protected the enzyme from this inhibition. The ATPase was specifically activated by Na+ or Li+ ions, markedly at high pH. After reconstitution into proteoliposomes, the enzyme catalyzed the ATP-dependent transport of Na+, Li+, or Hi+. Proton transport was specifically inhibited by Na+ or Li+ ions, indicating a competition between these alkali ions and protons for binding and translocation across the membrane. These experiments characterize the I. tartaricus ATPase as a new member of the family of FS-ATPases, which use Na+ as the physiological coupling ion for ATP synthesis.
Neumann
S
S
Mikrobiologisches Institut, Eidgenössische Technische Hochschule Zürich, Switzerland.
Matthey
U
U
Kaim
G
G
Dimroth
P
P
D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000201:enzymology; D007700:Kinetics; D008094:Lithium / Q000378:metabolism; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D046911:Macromolecular Substances; D010446:Peptide Fragments; D008094:Lithium; D012964:Sodium; D006180:Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase