A novel subunit of vacuolar H(+)-ATPase related to the b subunit of F-ATPases.
The subunit structure of the vacuolar H(+)-ATPase (V-ATPase) membrane sector is not entirely known. The proteolipid is the only subunit that has been implicated in the mechanism of energy transfer in the enzyme. We have identified a protein (M16) that co-purifies with the V-ATPase complex from bovine chromaffin granules. Information obtained from the amino acid sequence of a proteolytic fragment of M16 was used to clone a bovine adrenal cDNA encoding this protein. The cDNA encodes a hydrophilic protein of 118 amino acid residues with a calculated molecular mass of 13682Da. Amino acid sequence analysis revealed that M16 exhibits a significant homology to subunit b of F-ATPases. M16 is smaller than subunit b and contains no apparent transmembrane segment in its N terminus. The remainder of subunit b is related to M16 not only by its amino acid sequence but also in its predicted structure of helix-turn-helix. The structural and evolutionary implications of these findings are discussed.
Supekova
L
L
Roche Institute of Molecular Biology, Roche Research Center, Nutley, NJ 07110, USA.
Sbia
M
M
Supek
F
F
Ma
Y
Y
Nelson
N
N
D000313:Adrenal Medulla / Q000201:enzymology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002837:Chromaffin Granules / Q000201:enzymology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics; D016415:Sequence Alignment; D025262:Vacuolar Proton-Translocating ATPases; D014617:Vacuoles / Q000201:enzymology*
D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases