Synthesis and properties of cyclic gomesin and analogues

Machado A.; Fazio M.A.; Miranda A.; Daffre S.; Machini M.T.

Synthesis and properties of cyclic gomesin and analogues

Tipo

Artigo

Data de publicação

2012

Periódico

Journal of Peptide Science

Citações (Scopus)

14

Autores

Machado A.
Fazio M.A.
Miranda A.
Daffre S.
Machini M.T.

Resumo

Gomesin (Gm) was the first antimicrobial peptide (AMP) isolated from the hemocytes of a spider, the Brazilian mygalomorph Acanthoscurria gomesiana. We have been studying the properties of this interesting AMP, which also displays anticancer, antimalarial, anticryptococcal and anti-Leishmania activities. In the present study, the total syntheses of backbone-cyclized analogues of Gm (two disulfide bonds), [Cys(Acm)2,15]-Gm (one disulfide bond) and [Thr2,6,11,15,d-Pro9]-Gm (no disulfide bonds) were accomplished, and the impact of cyclization on their properties was examined. The consequence of simultaneous deletion of pGlu1 and Arg16-Glu-Arg18-NH2 on Gm antimicrobial activity and structure was also analyzed. The results obtained showed that the synthetic route that includes peptide backbone cyclization on resin was advantageous and that a combination of 20% DMSO/NMP, EDC/HOBt, 60°C and conventional heating appears to be particularly suitable for backbone cyclization of bioactive peptides. The biological properties of the Gm analogues clearly revealed that the N-terminal amino acid pGlu1 and the amidated C-terminal tripeptide Arg16-Glu-Arg18-NH2 play a major role in the interaction of Gm with the target membranes. Moreover, backbone cyclization practically did not affect the stability of the peptides in human serum; it also did not affect or enhanced hemolytic activity, but induced selectivity and, in some cases, discrete enhancements of antimicrobial activity and salt tolerance. Because of its high therapeutic index, easy synthesis and lower cost, the [Thr2,6,11,15,d-Pro9]-Gm analogue remains the best active Gm-derived AMP developed so far; nevertheless, its elevated instability in human serum may limit its therapeutic potential. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd. The present study expands the knowledge on chemical peptide synthesis and on SAR of gomesin (Gm), an antimicrobial β-hairpin disulfide-stabilized peptide. The results prove the efficiency of our protocols at 60°C using conventional heating for fast backbone cyclization and show that, although the insertion of such conformational constraint did not dramatically enhance antimicrobial activity or serum stability of Gm and its analogues, it led to selectivity and, in some cases, higher hemolytic activity and salt tolerance. © 2012 European Peptide Society and John Wiley & Sons, Ltd.