# Positively Selected Sites in Cetacean Myoglobins Contribute to Protein Stability

 Title: Positively Selected Sites in Cetacean Myoglobins Contribute to Protein Stability Author: Dasmeh, Pouria; Serohijos, Adrian; Kepp, Kasper P.; Shakhnovich, Eugene Isaacovitch Note: Order does not necessarily reflect citation order of authors. Citation: Dasmeh, Pouria, Adrian W. R. Serohijos, Kasper P. Kepp, and Eugene I. Shakhnovich. 2013. Positively selected sites in cetacean myoglobins contribute to protein stability. PLoS Computational Biology 9(3): e1002929. Full Text & Related Files: 3591298.pdf (1.762Mb; PDF) Abstract: Since divergence ∼50 Ma ago from their terrestrial ancestors, cetaceans underwent a series of adaptations such as a ∼10–20 fold increase in myoglobin (Mb) concentration in skeletal muscle, critical for increasing oxygen storage capacity and prolonging dive time. Whereas the $$O_2$$-binding affinity of Mbs is not significantly different among mammals (with typical oxygenation constants of ∼0.8–1.2 $$µM^{−1}$$), folding stabilities of cetacean Mbs are ∼2–4 kcal/mol higher than for terrestrial Mbs. Using ancestral sequence reconstruction, maximum likelihood and Bayesian tests to describe the evolution of cetacean Mbs, and experimentally calibrated computation of stability effects of mutations, we observe accelerated evolution in cetaceans and identify seven positively selected sites in Mb. Overall, these sites contribute to Mb stabilization with a conditional probability of 0.8. We observe a correlation between Mb folding stability and protein abundance, suggesting that a selection pressure for stability acts proportionally to higher expression. We also identify a major divergence event leading to the common ancestor of whales, during which major stabilization occurred. Most of the positively selected sites that occur later act against other destabilizing mutations to maintain stability across the clade, except for the shallow divers, where late stability relaxation occurs, probably due to the shorter aerobic dive limits of these species. The three main positively selected sites 66, 5, and 35 undergo changes that favor hydrophobic folding, structural integrity, and intra-helical hydrogen bonds. Published Version: doi:10.1371/journal.pcbi.1002929 Other Sources: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3591298/pdf/ Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:10629728 Downloads of this work: