Meeting Abstract

P1.127  Thursday, Jan. 3  Linking temperature adaptation and conservation of function with patterns of AB domain evolution in parvalbumin. WHITTINGTON, A.C.*; MOERLAND, T.S.; Florida State University; Florida State University whittington@bio.fsu.edu

Temperature is a key factor driving the evolution of proteins. Previous studies of enzymes have shown that orthologs from species acclimated to different thermal environments can maintain a relatively similar level of function at physiological temperatures. In general, the differences in amino acid sequence that are correlated with this conservation of function lie outside enzyme active sites. Study of parvalbumin ion-binding characteristics permits knowledge of thermal adaptation obtained from enzymes to be extended to non-catalytic proteins, which have not been examined as thoroughly. Parvalbumins are intracellular calcium-binding proteins of the EF-hand type. In muscle cells they serve as a calcium sink allowing more rapid unloading of troponin-C leading to faster contraction/relaxation cycles. Parvalbumins contain two functional, highly conserved, binding sites and one non-functional site, the AB domain. The non-functional AB domain has been implicated as a modulator of binding affinity for the two functional domains. Preliminary sequence examination among polar and non-polar fish species shows frequent substitutions between residues 3 and 37 of the AB domain, with a striking example being substitution of phenylalanine at position 3 in non-polar species with leucine in Antarctic species. We are developing a model that may help identify patterns of evolution driven by habitat temperature by reconstructing the ancestral sequence of parvalbumins and mapping them onto the three dimensional structure.