3W5B

Crystal structure of the recombinant SERCA1a (calcium pump of fast twitch skeletal muscle) in the E1.Mg2+ state

3W5B の概要

• エントリーDOI: 10.2210/pdb3w5b/pdb
• 関連するPDBエントリー: 3W5A 3W5C 3W5D
• 分子名称: SERCA1a, SODIUM ION, MAGNESIUM ION, ... (6 entities in total)
• 機能のキーワード: p-type atpase, hydrolase, calcium transport, calcium binding, atp binding, endoplasmic reticulum, sarcoplasmic reticulum, recombinant, metal transport
• 由来する生物種: Oryctolagus cuniculus
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 113740.22

構造登録者

Toyoshima, C.,Iwasawa, S.,Ogawa, H.,Hirata, A.,Tsueda, J.,Inesi, G. (登録日: 2013-01-27, 公開日: 2013-03-06, 最終更新日: 2013-03-27)

主引用文献

Toyoshima, C.,Iwasawa, S.,Ogawa, H.,Hirata, A.,Tsueda, J.,Inesi, G.
Crystal structures of the calcium pump and sarcolipin in the Mg2+-bound E1 state.
Nature, 495:260-264, 2013

PubMed Abstract: P-type ATPases are ATP-powered ion pumps that establish ion concentration gradients across biological membranes, and are distinct from other ATPases in that the reaction cycle includes an autophosphorylation step. The best studied is Ca(2+)-ATPase from muscle sarcoplasmic reticulum (SERCA1a), a Ca(2+) pump that relaxes muscle cells after contraction, and crystal structures have been determined for most of the reaction intermediates. An important outstanding structure is that of the E1 intermediate, which has empty high-affinity Ca(2+)-binding sites ready to accept new cytosolic Ca(2+). In the absence of Ca(2+) and at pH 7 or higher, the ATPase is predominantly in E1, not in E2 (low affinity for Ca(2+)), and if millimolar Mg(2+) is present, one Mg(2+) is expected to occupy one of the Ca(2+)-binding sites with a millimolar dissociation constant. This Mg(2+) accelerates the reaction cycle, not permitting phosphorylation without Ca(2+) binding. Here we describe the crystal structure of native SERCA1a (from rabbit) in this E1·Mg(2+) state at 3.0 Å resolution in addition to crystal structures of SERCA1a in E2 free from exogenous inhibitors, and address the structural basis of the activation signal for phosphoryl transfer. Unexpectedly, sarcolipin, a small regulatory membrane protein of Ca(2+)-ATPase, is bound, stabilizing the E1·Mg(2+) state. Sarcolipin is a close homologue of phospholamban, which is a critical mediator of β-adrenergic signal in Ca(2+) regulation in heart (for reviews, see, for example, refs 8-10), and seems to play an important role in muscle-based thermogenesis. We also determined the crystal structure of recombinant SERCA1a devoid of sarcolipin, and describe the structural basis of inhibition by sarcolipin/phospholamban. Thus, the crystal structures reported here fill a gap in the structural elucidation of the reaction cycle and provide a solid basis for understanding the physiological regulation of the calcium pump.

PubMed: 23455422
DOI: 10.1038/nature11899

実験手法

X-RAY DIFFRACTION (3.2 Å)