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Mass spectrometric investigation of Maltacines E1a and E1b—two members of the Maltacine family of peptide antibiotics
Author(s) -
Hagelin Gunnar
Publication year - 2005
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.2238
Subject(s) - chemistry , protonation , peptide , residue (chemistry) , stereochemistry , bacillus subtilis , mass spectrometry , molecule , cyclic peptide , amino acid , ring (chemistry) , ion , chromatography , organic chemistry , bacteria , biochemistry , biology , genetics
We have recently described the discovery of the Maltacines—a new family of cyclic peptide antibiotics from Bacillus subtilis . In this paper the mass spectrometric characterisation of two of the members is reported. A chemoselective ring opening with base to give the linear peptides was necessary before mass spectrometric characterisation could be performed. MS n of the singly and doubly charged protonated molecules gave uninterrupted series of Bn and Y″n ions that allowed determination of the amino acid sequence. By using a combination of derivatisation with phenylisothiocyanate (PITC), high‐resolution mass spectrometry and H/D exchange, the identities of three unknown residues were determined. The nature and position of the cyclic structure were disclosed by a chemoselective ring opening with Na 18 OH and it was found to be a lactone formed between a hydroxyl of residue number 4 and the C‐terminal amino acid number 12. Peptides with different combinations of P/Q and P/K at the N‐terminus were synthesised to verify the sequence of the N‐terminal B 2 ion. The structure of the two peptides is proposed to be: E1a: cyclo‐4,12(P‐Q‐Y‐Adip‐V‐E‐T‐Y‐Orn‐S‐Y‐I‐OH) and E1b: cyclo‐4,12(P‐Q‐Y‐Adip‐V‐E‐T‐Y‐K‐S‐Y‐I‐OH). Adip = (2‐amino‐4,5‐dihydroxypentanoic acid). Copyright © 2005 John Wiley & Sons, Ltd.