The proteolipid of the A(1)A(0) ATP synthase from Methanococcus jannaschii has six predicted transmembrane helices but only two proton-translocating carboxyl groups.
The proteolipid, a hydrophobic ATPase subunit essential for ion translocation, was purified from membranes of Methanococcus jannaschii by chloroform/methanol extraction and gel chromatography and was studied using molecular and biochemical techniques. Its apparent molecular mass as determined in SDS-polyacrylamide gel electrophoresis varied considerably with the conditions applied. The N-terminal sequence analysis made it possible to define the open reading frame and revealed that the gene is a triplication of the gene present in bacteria. In some of the proteolipids, the N-terminal methionine is excised. Consequently, two forms with molecular masses of 21,316 and 21,183 Da were determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The molecular and biochemical data gave clear evidence that the mature proteolipid from M. jannaschii is a triplication of the 8-kDa proteolipid present in bacterial F(1)F(0) ATPases and most archaeal A(1)A(0) ATPases. Moreover, the triplicated form lacks a proton-translocating carboxyl group in the first of three pairs of transmembrane helices. This finding puts in question the current view of the evolution of H(+) ATPases and has important mechanistic consequences for the structure and function of H(+) ATPases in general.
Ruppert
C
C
Lehrstuhl für Mikrobiologie der Ludwig-Maximilians-Universität München, Maria-Ward-Strasse 1a, 80638 München, Germany.
Kavermann
H
H
Wimmers
S
S
Schmid
R
R
Kellermann
J
J
Lottspeich
F
F
Huber
H
H
Stetter
K O
KO
Müller
V
V
D013058:Mass Spectrometry; D017017:Methanococcus / Q000737:chemistry* / Q000378:metabolism; D017510:Protein Folding; D011510:Proteolipids / Q000737:chemistry*; D017494:Proton Pumps / Q000737:chemistry / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism
D011510:Proteolipids; D017494:Proton Pumps; D006180:Proton-Translocating ATPases