Abstracts of papers at the Fifty-Ninth Annual Meeting of the Society of General Physiologists

1. SR Ca²⁺-ATPase Atomic Structure and Molecular Dynamics Simulations. YUJI SUGITA and CHIKASHI TOYOSHIMA, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo, Japan (Sponsor: David Gadsby)

Sarcoplasmic reticulum (SR) Ca²⁺ATPase (SERCA1a) is an integral membrane protein of 110 kD that establishes the concentration gradient of Ca²⁺ across the SR membrane by transporting two Ca²⁺ per ATP hydrolyzed. Recent X-ray structures of SR Ca²⁺-ATPase provide atomic models for two high-affinity Ca²⁺-binding sites in the transmembrane region, which consists of 10 helices. We have studied how the Ca²⁺-binding sites are stabilized in the transmembrane region by using all-atom molecular dynamics (MD) simulations with explicit solvent and lipids. During the simulations, three cytoplasmic domains as well as the transmembrane domain were very stable. However, the Ca²⁺-coordination and the H-bonds formed by the protonation of Glu58...