Identification and characterization of peptides which bind Cryptococcus neoformans melanin

Cryptococcus neoformans is a ubiquitous yeast-like fungus of major medical importance. One of the virulence factors of C. neoformans is the production of melanin. Despite advances in the understanding of the mechanisms by which melanin provides survival advantages to the fungus, little is known about the polymer itself. To investigate surface properties of melanin and to generate novel reagents for the study of melanogenesis, we used a random decapeptide phage display library to screen for melanin binding peptides. ELISA and immunohistochemical techniques were developed to detect melanin binding peptides. The results indicate that 1) melanin binding peptides exist; 2) the selected peptides contain a high proportion of positively charged and aromatic residues; and 3) melanin binding peptides can be used to detect the polymer in melanized C. neoformans cells. The findings are consistent with and supportive of a previous report that melanin is negatively charged and suggest that the peptides can be used to study melanogenesis in C. neoformans.