The evolution of orthologous genes coding for -defensin 2 (BD2) in primates has been subject to positive
selection during the divergence of the platyrrhines from the catarrhines and of the Cercopithecidae from the
Hylobatidae, great apes, and humans. Three peptides have been selected for a functional analysis of the effects
of sequence variations on the direct antimicrobial activity: human BD2 (hBD2), Macaca fascicularis BD2
(mfaBD2), and a variant of the human peptide lacking Asp4, (D)hBD2, which is characteristic only of the
human/great ape peptides. hBD2 and mfaBD2 showed a significant difference in specificity, the former being
more active towards Escherichia coli and the later towards Staphylococcus aureus and Candida albicans. Asp4 in
the human peptide appears to be important, as (D)hBD2 was less structured and had a markedly lower
antimicrobial activity. The evolution of -defensin 2 in primates may thus have been driven, at least in part,
by different environmental pressures so as to modulate antimicrobial activity.
