Molecule and Gene of Sulfolobus acidocaldarius ATPase
A novel ATPase (Sul-ATPase) was solubilized from membranes of an archaebacterium, Sulfolobus acidocaldarius, by washing with a buffer containing EDTA. Enzymatic characteristics of this ATPase are distinctly different from F1-ATPase and resemble eukaryotic endomembrane H+-ATPase. Attempt was made to isolate the whole ATPase complex from membranes using a detergent and the isolated complex showed several protein bands in SDS-PAGE including a band at the position around 40KD in addition to subunits of water-soluble Sul-ATPase. By the same procedure to isolate proteolipid subunit, or Foc subunit, of F0F1-ATPase, a very hydrophobic protein was extracted from membranes of this bacterium by chloroform-methanol treatment. [14C]DCCD bound to this protein when the membrane was incubated with this reagent. Molecular cloning of the Sul-ATPase operon revealed that the α and β subunits of Sul-ATPase show a remarkable amino acid sequence homology to the 70K and 60K subunits of eukaryotic vacuolar H+-ATPases, respectively. They also show significant, though less remarkable, homology to the α and β subunits of F0F1-ATPase. The operon also contains a gene encoding the proteolipid subunit above mentioned. Its sequence clearly shows that it is a Sulfolobus equivalence of Foc subunit. From the analysis of the sequences, a phylogenetic tree of evolution of H+-ATPases was constructed and we propose the monomeric H+-ATPase as the most primordial H+-ATPase. If it is really the case, cooperative kinetics observed for F0F1 -ATPases are related to some regulatory functions which were added to the core catalytic function later in evolution. Close relation between archaebacterial ATPases and the eukaryotic endomembrane H+-ATPases also implies that the eukaryotic endomembrane system has been originated from inclusion of the plasma membranes of an ancestral archaebacterial cell. At the standpoint of symbiotic theory of the origin of eukaryote, above proposition means that the host cell for symbionts was an ancestral archaebacterial cell.
KeywordsPartial Amino Acid Sequence ATPase Complex Sulfolobus Acidocaldarius Host Cell Plasma Membrane Proteolipid Subunit
Unable to display preview. Download preview PDF.
- 4.Senior, A.E. (1990) Ann. Rev. Biophys. in pressGoogle Scholar
- 13.Konishi, J., Denda, K., Oshima, T., Wakagi, T., Uchida, E., Ohsumi, Y., Anraku, Y., Matsumoto, T., Wakabayashi, T., Mukohata, Y., Ihara, K., Inatomi, K., Kato, K., Ohta, T., Allison, W.S., and Yoshida, M. (1989) J. Biochem. in pressGoogle Scholar
- 14.Sebald, W. and Hoppe, J. (1981) Curr. Top. Bioenerg. 12, 1–64Google Scholar