Photoinduced generation of dityrosine by the lasso-peptide microcin J25

GALVAN, E; CHALON, M; MINAHK, C; BELLOMIO, A

Santiago del Estero

Congreso; XLIV Reunión Anual SAB 2015; 2015

Sociedad Argentina de Biofísica

Microcin J25 (MccJ25) is a 21 amino-acid peptide (G1-G-A-G-H5-V-P-E-Y-F10-V-G-I-G-T15-P-I-S-F-Y20-G) that adopts a highly stable lasso-like structure, which consists of an 8-residues ring formed between the N-terminal Gly1 and the side chain of Glu8 with the C-terminal ?tail? (Tyr9-Gly21) passing through the ring. MccJ25 is produced by Escherichia coli and has two cellular targets, i.e. the RNA polymerase and the membrane respiratory chain. It displays bactericidal activity against several Gram-negative food-borne pathogens, including Salmonella, Shigella and E. coli. Among the available MccJ25 mutants, Y9F variant (Tyr9 substituted by phenylalanine) is still active on RNAP but it loses the ability to overproduce superoxide hence being unable to inhibit oxygen consumption. It was demonstrated that the two tyrosines (Tyr9 and Tyr20) were involved in an irreversible oxidation process but only the Tyr9 peptide was associated to the tyrosil radical formation [1]. In this work we generated MccJ25 tyrosyl radical by blue light photosensitization with the consequent formation of Tyr-Tyr bonds. The MccJ25 with Tyr-Tyr bonds was purified by reversed phase chromatography and it was characterized by different techniques. Furthermore, its antimicrobial activity was evaluated.