The AFP from the fungi kingdom is under strong positive natural selection

Fungal cells can colonize, virtually, in any surface of the planet and infect almost any multi cellular organism. Over the last few years, fungal infections in human patients have grown incredibly and the number of cases of deaths due to fungal infection in immunocompromised patients are surprisingly high. More than 300 species of fungus cause human diseases and a large number of commensal species are the cause of allergic reactions. Evolution has driven mechanisms associated with bio control agents produced either by fungus or other species. The antifungal protein precursor is a small biological entity with antimicrobial activity. Many species of fungus are able to produce this protein. has been pointed out as a possible antifungal drug because it destroy pathogenic fungi but has no effect on mammalian cells. In the present paper, we analyze the AFP nucleotide sequence of 61 fungal species in order to identify if natural selection is indeed acting upon AFP through dN/dS ration (number of non-synonymous and synonymous substitutions). We further discuss if selection is acting upon a specific site of the AFP nucleotide sequence. Our results show that selection is acting on the codon level of AFP, which means that there is a higher proportion of amino acid substitution in the population studied with dN/dS> 1. We hypothesize that the site 63 is an important region of variation of fungi AFP and could significantly contribute to the function of the protein and stabilization of PPIs and protein-membrane interaction. As a perspective for future projects, we are going to assess in silico mutation at site 63 and perform dynamical simulation in order to check if this specific site is essential for the conformational structure and function of AFP.

Keywords: dN/dS; AFP; natural selection; Bioinformatics.