engleski

Bovine neutrophil antibiotic peptides and their precursors : structure and role in innate immunity

Four peptides were characterized in extracts of bovine neutrophil granules: an Arg-rich dodecapeptide, maintained in a cyclic structure by a disulfide bridge ; a Trp-rich tridecapeptide named indolicidin ; and two 43- and 59 amino acids long peptides, named Bac5 and Bac7, with frequent repeats of the triplets Arg-Pro-Pro and Pro-Arg-Pro, respectively. The full length cDNA of the first three of these peptides was characterized recently. Sequence analysis showed that the prosequences of the predicted precursors of all the three peptides are highly identical and exhibited also a remarkable similarity to cathelin, a porcine inhibitor of cathepsin L. Purified proBac5 actually proved in in vitro assays to inhibit cathepsin L, but not other cysteine proteinases such as cathepsin B. Unlike proBac5, proBac7 is selectively chemotactic to monocytes. Several fragments of Bac5 and Bac7 (from 6 to 35 residues) were synthesized by the Fmoc method. The results of antibacterial assays show that the N-terminal portion, the most cationic one in both Bac5 and Bac7, is essential for the antimicrobial activity and that the minimal length necessary to arrest the growth of susceptible bacteria is 18-20 residues.

permeability-increasing protein; antimicrobial polypeptides; antibacterial peptides; bactenecins; defensins; inhibitor; granules; sequence; cdna; dodecapeptide

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