Verification of protein sequence by fast atom bombardment mass spectrometry. Amino acid sequence of protein S, a development-specific protein of Myxococcus xanthus.

A mass spectrometric method was applied to protein S, a development-specific protein of Myxococcus xanthus, in order to verify the amino acid sequence deduced from the nucleotide sequence of its gene. On examining proteolytic digests of the protein by fast atom bombardment mass spectrometry without separation of individual peptides, signals corresponding to individual peptides were observed in the mass spectra. The mass values of the observed signals were correlated to the theoretical mass values calculated from the predicted amino acid sequence, thereby identifying the peptides and proving the accuracy of the sequence. The previous finding that protein S is the product of the second gene of the two tandemly repeated genes on the M. xanthus chromosome ( Inouye , S., Franceschini , T., and Inouye , M. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 6829-6833) is now unambiguously confirmed.