Cabras T, Longhi R, Secundo F, Nocca G, Conti S, Polonelli L, Fanali C, Inzitari R, Petruzzelli R, Messana I, Castagnola M, Vitali A
Department of Sciences Applied to Biosystems, University of Cagliari, Cittadella Universitaria, Monserrato I-09042, Cagliari, Italy.
J Pept Sci. 2008 Mar;14(3):251-60. doi: 10.1002/psc.914.
A 1905-Da cationic proline-rich peptide, named SP-B, was recently isolated by our group as the main component of salivary gland granules, and its primary sequence fully characterized by means of automated Edman sequencing and LC-MS/MS tools. In the present study SP-B is shown to possess antifungal activity when challenged with strains of Cryptococcus neoformans, Candida albicans and Aspergillus fumigatus, while only negligible antibacterial activity was detected. Furthermore, SP-B was found to be non-cytotoxic when tested on fibroblast cell lines. To obtain information regarding its structure affinity, capillary electrophoresis (CE), circular dichroism (CD) and attenuated total reflection (ATR)-FT/IR experiments were performed. CE revealed a pH dependence of the hydrodynamic radial dimensions both in aqueous and 2,2,2-trifluoroethanol solutions. CD and ATR-FT/IR measurements confirmed the structure-pH relationship, revealing a secondary structure composed of mixed proportions of polyproline-II, unordered and turn motifs, the last being more evident in the zwitterionic form of the peptide. From these findings SP-B peptide could be classified as a new member of the proline-rich antimicrobial peptide family.
