el-Hayek R, Antoniu B, Wang J, Hamilton S L, Ikemoto N
Boston Biomedical Research Institute, Massachusetts 02114, USA.
J Biol Chem. 1995 Sep 22;270(38):22116-8. doi: 10.1074/jbc.270.38.22116.
In an attempt to identify and characterize functional domains of the rabbit skeletal muscle dihydropyridine receptor alpha 1 subunit II-III loop, we synthesized several peptides corresponding to different regions of the loop: peptides A, B, C, C1, C2, D (cf. Fig. 1). Peptide A (Thr671-Leu690) activated [3H]ryanodine binding to, and induced Ca2+ release from, rabbit skeletal muscle triads, but none of the other peptides had such effects. Peptide A-induced Ca2+ release and activation of ryanodine binding were partially suppressed by an equimolar concentration of peptide C (Glu724-Pro760) but were not affected by the other peptides. These results suggest that the short stretch in the II-III loop, Thr671-Leu690, is responsible for triggering SR Ca2+ release, while the other region, Glu724-Pro760, functions as a blocker of the release trigger. A hypothesis is proposed to account for how these subdomains interact with the sarcoplasmic reticulum Ca2+ release channel protein during excitation-contraction coupling.
为了鉴定和表征兔骨骼肌二氢吡啶受体α1亚基II-III环的功能结构域，我们合成了对应于该环不同区域的几种肽：肽A、B、C、C1、C2、D（参见图1）。肽A（Thr671-Leu690）激活了[3H]ryanodine与兔骨骼肌三联体的结合，并诱导了Ca2+从三联体中释放，但其他肽均无此作用。等摩尔浓度的肽C（Glu724-Pro760）可部分抑制肽A诱导的Ca2+释放和ryanodine结合的激活，但其他肽对其无影响。这些结果表明，II-III环中的短片段Thr671-Leu690负责触发肌浆网Ca2+释放，而另一个区域Glu724-Pro760则作为释放触发的阻断剂发挥作用。我们提出了一个假设，以解释这些亚结构域在兴奋-收缩偶联过程中如何与肌浆网Ca2+释放通道蛋白相互作用。
