Conservation of complete trimethylation of lysine-43 in the rotor ring of c-subunits of metazoan adenosine triphosphate (ATP) synthases.
Bottom Line: In the twenty-nine metazoan species that have been examined, the complete methylation of lysine-43 is conserved, and it is likely to be conserved throughout the more than two million extant metazoan species.In unicellular eukaryotes and prokaryotes, when the lysine is conserved it is unmethylated, and the stoichiometries of c-subunits vary from 9-15.One possible role for the trimethylated residue is to provide a site for the specific binding of cardiolipin, an essential component of ATP synthases in mitochondria.
Affiliation: From the ‡Mitochondrial Biology Unit, Medical Research Council, Hills Road, Cambridge, CB2 0XY, United Kingdom and.Show MeSH
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Mentions: The molecular masses of c-subunits (Table I) were determined by liquid chromatography (LC)-ESI-MS by a procedure that included a reverse-phase chromatographic fractionation compatible with membrane proteins (29). A representative mass spectrum of an intact c-subunit is presented in Fig. 2. As the masses of many metazoan c-subunits are known from their sequences, the measured and calculated values were compared (Table I), and in each case the measured mass of the intact protein exceeded the calculated value by 42 ± 1 Da, indicating that either an acetyl group or three methyl groups had been added to the protein post-translationally. The sequences of the c-subunits of the brush tailed possum, T. vulpecula, the spur-thighed tortoise, T. graeca, the European sea bass, D. labrax, and the spiny dogfish, S. acanthias, have not been reported, but their measured masses are also very similar to the values in other vertebrates, suggesting that both their sequences and the protein modification are conserved. No sequences are available currently for the c-subunits from eight other species in Table I, but in four instances the sequences are known in closely related species, and the data suggest that the orthologs have identical sequences and are modified in the same way. Thus, the observed mass of the c-subunit in the North Atlantic mussel, M. edulis, exceeds by 42 Da the calculated value for the Mediterranean mussel, M. galloprovincalis, as do the measured masses of the c-subunits of the New Zealand sea urchin (or kina), E. chloroticus, in comparison with the calculated value in the Pacific purple sea urchin, Stronglyocentrotus purpuratus, and of the c-subunit from the earthworm, L. terrestis, in comparison with the calculated value from the red earthworm, L. rubellus. Moreover, the measured value of 7684 Da for the c-subunit in the cabbage looper moth, T. ni, is 42 Da greater than the calculated values for two other lepidopterans, the fall armyworm, Spodoptera frugipera, and the tobacco hornworm, Manduca sexta, indicative of identical sequences and modification of the c-subunits in these three lepidopterans. In contrast, the measured masses of c-subunits in the European lobster, H. gammarus, the brown crab, C. pagarus, the Australasian sea cucumber, A. mollis and the brine shrimp, A. salina, do not correspond to the values in any closely related species. The amounts of c-subunits purified from B. constrictor and C. incrustans were insufficient to permit the masses of the intact proteins to be measured.
Affiliation: From the ‡Mitochondrial Biology Unit, Medical Research Council, Hills Road, Cambridge, CB2 0XY, United Kingdom and.