Glycine 105 as Pivot for a Critical Knee-like Joint between Cytoplasmic and Transmembrane Segments of the Second Transmembrane Helix in Ca2+-ATPase.

ABSTRACT: The cytoplasmic actuator domain of the sarco(endo)plasmic reticulum Ca²⁺-ATPase undergoes large rotational movements that influence the distant transmembrane transport sites, and a long second transmembrane helix (M2) connected with this domain plays critical roles in transmitting motions between the cytoplasmic catalytic domains and transport sites. Here we explore possible structural roles of Gly¹⁰⁵ between the cytoplasmic (M2c) and transmembrane (M2m) segments of M2 by introducing mutations that limit/increase conformational freedom. Alanine substitution G105A markedly retards isomerization of the phosphoenzyme intermediate (E1PCa₂ → E2PCa₂ → E2P + 2Ca²⁺), and disrupts Ca²⁺ occlusion in E1PCa₂ and E2PCa_2</

SUBMITTER: Daiho T 

PROVIDER: S-EPMC5114418 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature