Abramson J J, Mullen S P, Koehler S, Mansoor D, Anderson P, Wamser C C, Swan T J, Favero T G
Department of Physics, Portland State University, Portland, Oregon 97207, USA.
Arch Biochem Biophys. 2001 Jul 15;391(2):235-44. doi: 10.1006/abbi.2001.2403.
o-Phthalaldehyde (OPA) is a bifunctional reagent that forms an isoindole derivative by reacting with cysteine and lysine residues separated by approximately 0.3 nm. OPA inhibits sarcoplasmic reticulum (SR) Ca(2+)-ATPase activity at low micromolar concentrations and induces Ca(2+) release from actively loaded SR vesicles by activating the ryanodine receptor from fast twitch skeletal muscle. Both ryanodine binding and single-channel activity show a biphasic concentration dependence. At low OPA concentrations (<100 microM), ryanodine binding and single channel activity are stimulated, while at higher concentrations, a time-dependent sequential activation and inhibition of receptor binding is observed. Activation is characterized by a Ca(2+)-independent increase in maximal receptor occupancy. Data are presented to support a model in which Ca(2+) channel and ryanodine binding activity are enhanced due to an intramolecular cross-linking of nearby lysine and nonhyperreactive cysteine residues. OPA complexation with endogenous lysine residue(s) is critical for receptor activation.
邻苯二甲醛（OPA）是一种双功能试剂，它通过与相隔约0.3纳米的半胱氨酸和赖氨酸残基反应形成异吲哚衍生物。OPA在低微摩尔浓度下抑制肌浆网（SR）Ca(2+) - ATP酶活性，并通过激活快肌骨骼肌的兰尼碱受体诱导从主动加载的SR囊泡中释放Ca(2+)。兰尼碱结合和单通道活性均表现出双相浓度依赖性。在低OPA浓度（<100 microM）时，兰尼碱结合和单通道活性受到刺激，而在较高浓度时，观察到受体结合的时间依赖性顺序激活和抑制。激活的特征是最大受体占有率的Ca(2+)非依赖性增加。本文提供的数据支持一种模型，即由于附近赖氨酸和非高反应性半胱氨酸残基的分子内交联，Ca(2+)通道和兰尼碱结合活性增强。OPA与内源性赖氨酸残基的络合对于受体激活至关重要。
