N-terminal amino acid sequences of the subunits of the Na(+)-translocating F1F0 ATPase from Propionigenium modestum.

We report here the N-terminal protein sequences of the subunits of the ATPase from Propionigenium modestum. Subunits c, b, delta, alpha and beta start with an N-terminal methionine residue, the gamma and epsilon subunits have an alanine N-terminus, from which N-formylmethionine was hydrolyzed by posttranslational modification, and subunit a contains a blocked N-terminus. Each of the N-terminal sequences exactly matches a portion of the DNA sequence in the gene encoding the respective subunit protein on the unc operon. Thus, the exact translational start for each subunit protein can be identified and the primary structures of the protein transcripts can be clearly defined. Based on these data the putative size of the open reading frame that was envisaged from the DNA sequence had to be revised for the alpha and delta subunits.