Structure, function, and evolution of Gga -AvBD11, the archetype of the structural avian-double-β-defensin family (original) (raw)

Out of the 14 avian β-defensins identified in the Gallus gallus genome, only 3 are present in the chicken egg, including the egg-specific avian β-defensin 11 ( Gga -AvBD11). Given its specific localization and its established antibacterial activity, Gga -AvBD11 appears to play a protective role in embryonic development. Gga -AvBD11 is an atypical double-sized defensin, predicted to possess 2 motifs related to β-defensins and 6 disulfide bridges. The 3-dimensional NMR structure of the purified Gga- AvBD11 is a compact fold composed of 2 packed β-defensin domains. This fold is the archetype of a structural family, dubbed herein as avian-double-β-defensins (Av-DBD). We speculate that AvBD11 emanated from a monodomain gene ancestor and that similar events might have occurred in arthropods, leading to another structural family of less compact DBDs. We show that Gga -AvBD11 displays antimicrobial activities against gram-positive and gram-negative bacterial pathogens, the avian protozoan E...