Molecular Evolution of H+-ATPases. I. Methanococcus and Sulfolobus are Monophyletic with Respect to Eukaryotes and Eubacteria
2014
Gogarten, Johann Peter | Rausch, Thomas | Bernasconi, Paul | Kibak, Henrik | Taiz, Lincoln
The classification of methanogenic bacteria as archaebacteria based on 16 s rRNA sequence analysis is currently in dispute. To provide an alternative molecular marker, the polymerase chain reaction technique was used to amplify a 930 bp fragment of Methanococcus thermolithotrophicus genomic DNA corresponding to the catalytic domain of the membrane H⁺ -ATPase. The deduced amino acid sequence was 54-58% identical to the ~ 70 kDa subunits of Sulfolobus acidocaldarius and the eukaryotic vacuolar-type H⁺-A T P ase, and only 29% identical to the beta subunit of the eubacterial-type F₀F₁-ATPases. Interestingly, a highly conserved aspartate residue in the phosphorylation domain of E 1 E 2-A TPases (P-type) is conserved in the Methanococcus sequence, but is absent from all other known vacuolar and F₀F₁-ATPases. This suggests that the H⁺-ATPase of M. thermolithotrophicus, like that of M. voltae, may have a phosphorylated intermediate, despite belonging to the vacuolar-type class of proton pumps. Phylogenetic analysis using Felsenstein’s maximum likelihood method and Lake’s evolutionary parsimony method confirmed that the H⁺- ATPases of the two archaebacteria, Methanococcus and Sulfolobus, when compared to eukaryotic vacuolar-type ATPases and eubacterial F₀F₁₋ATPases, form a monophyletic group.
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