title: Structure investigation of Maltacine D1a, D1b and D1c-cyclic peptide lactones of the Maltacine complex from Bacillus subtilis.
abstract: A new complex of cyclic peptide lactone antibiotics from Bacillus subtilis, which we named Maltacines has recently been described. The structure elucidation of three of them is reported in this paper. The amino acid sequences and structures of the peptides were found by MS(n) of the ring-opened linear peptides that gave uninterrupted sequences of Bn and Y''n ions. The identities of four unknown residues in the sequences were solved by a combination of derivatisation with phenylisothiocyanate (PITC), high-resolution mass spectrometry and H/D exchange. The nature and position of the cyclic structure was disclosed by a chemo-selective ring opening with Na18OH and was found to be a lactone formed between a hydroxyl of residue number 4 and the C-terminal amino acid number 12. For verification of the structure of the B2 + ion, peptides with different combinations of P/Q and P/K at the N-terminus were synthesized. The structures of the four peptides is tentatively suggested to be: D1a: cyclo(4,12)-P-Q-Y-Adip-A-E-T-Y-Orn-HGly-Y-I-OH, D1b: cyclo(4,12)-P-Q-Y-Adip-A-E-T-Y-Orn-S-Y-I-OH and D1c: cyclo(4,12)-P-Q-Y-Adip-A-E-T-Y-K-S-Y-I-OH. Adip = aminodihydroxy pentanoic acid and HGly = hydroxyglycine.
authors.affiliation: MYCOCOMB, Arnulf Øverlands vei 185, 0764 Oslo, Norway. gunnarhagelin@ge.com
authors.forename: Gunnar
authors.initials: G
authors.lastname: Hagelin
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000737:chemistry* / Q000378:metabolism; D007783:Lactones / Q000737:chemistry*; D008832:Microchemistry / Q000379:methods; D008969:Molecular Sequence Data; D015394:Molecular Structure; D036103:Nanotechnology; D010456:Peptides, Cyclic / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
chemical_list: D007783:Lactones; D010456:Peptides, Cyclic