Lennon N J, Harmon S, Mackey A, Ohlendieck K
Department of Pharmacology, National University of Ireland, University College Dublin, Belfield.
Mol Cell Biol Res Commun. 1999 Jun;1(3):182-7. doi: 10.1006/mcbr.1999.0129.
The slow/cardiac isoform of the sarcoplasmic reticulum Ca2+-ATPase plays an important role in cardiac muscle Ca2+-homeostasis. To determine the native configuration of the SERCA2 ion pump, a chemical cross-linking analysis of heart microsomes was performed. Using one- and two-dimensional immunoblotting following incubation with the hydrophilic probe bis-sulfosuccinimidyl suberate or the hydrophobic crosslinker dithiobis-succinimidyl-propionate, we demonstrate here that SERCA2 forms high-molecular-mass aggregates. In contrast to the Na+/Ca2+-exchanger, Ca2+-ATPase clusters can be stabilized by hydrophilic 1.2 nm crosslinkers and are sensitive to chemical reduction. Hence, the native form of this important Ca2+-regulatory membrane protein involved in cardiac muscle relaxation appears not to exist as a monomeric ion pump unit. Protein-protein interactions might play an important role in the physiological functioning of this Ca2+-ATPase isoform, as has previously been shown for skeletal muscle Ca2+-pumps, Ca2+-binding proteins and Ca2+-channels.
肌浆网Ca2+-ATP酶的慢/心脏亚型在心肌Ca2+稳态中起重要作用。为确定SERCA2离子泵的天然构象，对心脏微粒体进行了化学交联分析。在用亲水性探针双（磺基琥珀酰亚胺）辛二酸酯或疏水性交联剂二硫代双（琥珀酰亚胺基）丙酸酯孵育后，通过一维及二维免疫印迹法，我们在此证明SERCA2形成高分子量聚集体。与Na+/Ca2+交换体不同，Ca2+-ATP酶聚集体可被亲水性1.2 nm交联剂稳定，且对化学还原敏感。因此，这种参与心肌舒张的重要Ca2+调节膜蛋白的天然形式似乎并非以单体离子泵单元存在。蛋白质-蛋白质相互作用可能在这种Ca2+-ATP酶亚型的生理功能中起重要作用，正如先前在骨骼肌Ca2+-泵、Ca2+-结合蛋白及Ca2+-通道中所显示的那样。
