A revised primary structure for neocarzinostatin based on fast atom bombardment and gas chromatographic-mass spectrometry.

The amino acid sequence of the antitumor protein neocarzinostatin was revised on the basis of mass spectrometric studies. Gas chromatographic mass spectrometry on the O-trimethylsilyl polyaminoalcohol derivatives of peptide mixtures derived from tetra S-carboxymethyl-neocarzinostatin were used to partially sequence neocarzinostatin. In addition, fast atom bombardment-mass spectrometric experiments on neocarzinostatin and its tryptic fragments gave the molecular weights of various peptides and, in some cases, partial sequence information. The revised sequence involved reordering of two chymotryptic peptides, the identification of a new di- and tripeptide sequence (Ala-Asp and Ala-Ser-Thr), the repositioning of Trp at position 39, and the assignment of the remaining Asx residues. The revised structure for neocarzinostatin (Mr = 11,105) now shows considerable homology with the other antitumor antibiotic proteins macromomycin and actinoxanthin.