Structural and functional analyses confirm the presence of functional P‐loops and intrinsic GTPase activity in Evc protein (1013.9)

Abstract

Ellis van Creveld (EvC) syndrome is a rare multi‐symptom human genetic disorder clinically characterized by mild short stature, postaxial polydactyly, dysplastic nail and teeth. Evc is one of the novel proteins that have been implicated in the pathogenesis of EvC syndrome and its milder form, Weyers acrofacial dysostosis (WAD). Mutations in EVC and EVC2 genes that cause these syndromes introduce premature termination codons and frameshifts, resulting in production of defective Evc and Evc2 proteins respectively. Genetic and biochemical experiments have identified Evc and Evc2 as novel proteins that are essential for positive regulation of both Indian and sonic hedgehog (Hh) signaling pathways during bone and heart development, and pathogenesis of EvC syndrome. Two separate research reports demonstrated that Evc‐Evc2 complex interacts with smoothened (smo) at the base of the cilia to transduce Hh‐induced signal to downstream proteins. We present spectroscopic and structural evidence to show that the putative P‐loop motif in Evc is functional and that it confers GTPase activity on the protein. The implications of our findings on the mechanism of transduction and regulation of Hh‐induced signals will be discussed.