An immunological approach to myosin light-chain function in thick filament linked regulation. 2. Effects of anti-scallop myosin light-chain antibodies. Possible regulatory role for the essential light chain.
An immunological approach to myosin light-chain function in thick filament linked regulation. 2. Effects of anti-scallop myosin light-chain antibodies. Possible regulatory role for the essential light chain.
复制标题
粗丝连接调节中肌球蛋白轻链功能的免疫学方法。
DOI：
10.1021/bi00508a021
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发表时间：
1981
期刊：
影响因子：
2.9
通讯作者：
Szent-Györgyi,AG
中科院分区：
文献类型：
--
作者：
Wallimann,T;Szent-Györgyi,AG
Theo Wallimann和Andrew G. Szent-Gyorgyi* 摘要：针对扇贝肌球蛋白的调节轻链（R-LC）或必需轻链（SH-LC）的特异性抗体通过在缺乏钙的情况下提高肌动蛋白激活的Mg ~（2+）-ATP酶活性来消除肌原纤维、肌球蛋白和重肌球蛋白中的钙调节。在每个肌球蛋白结合2.5-3个抗体的摩尔比下，钙依赖性完全消除。单价抗R-LC Fab和抗SH-LC Fab片段也可使肌原纤维完全脱敏。高Ca ~（2+）-ATP酶活性不受抗体的影响。抗SH-LC IgG在钙和钾激活的乙二胺四乙酸（EDTA）-ATP酶活性的存在下降低约一半的肌动蛋白激活的Mg ~（2+）-ATP酶。然而，抗SH-LC Fab脱敏而不抑制肌动蛋白激活的Mg 2 +-ATP酶。两种抗体的脱敏作用被取消了事先吸收同源肌球蛋白轻链。钙结合和R-LC含量保持不受抗R-LC和抗SH-LC IgG以及抗SH-LC Fab的影响。抗R-LC Fab片段诱导R-LC与肌原纤维和肌球蛋白的显著（70%）解离，同时伴有钙结合的损失。相反，抗R-LC IgG阻止EDTA使R-LC与肌球蛋白解离。抗R-LC IgG与肌原纤维的结合与其R-LC含量成比例。增加量的抗SH-LC IgG被缺乏R-LC的肌原纤维结合。结合的抗SH-LC抗体显著抑制EDTA处理的肌原纤维对R-LC的再摄取以及抗R-LC抗体的完全结合。某些兔产生了一群抗SH-LC抗体，它们对这种轻链具有特异性，并广泛地与肌球蛋白结合，但不能使其脱敏（非脱敏性抗SH-LC抗体）。脱敏性和非脱敏性抗SH-LC IgG群与肌球蛋白上SH-LC的不同区域结合，两种抗体与SH-LC的结合几乎是相加的。非致密化SH抗体抑制R-LC的再摄取较少，其与肌原纤维的结合不受R-LC的存在的影响。这些研究表明SH-LC直接或间接参与肌球蛋白相关的调节，提高了R-LC和SH-LC之间相互作用的可能性，并证实了扇贝R-LC的调节功能。两种类型的轻链的相对位置和肌球蛋白的亚片段-2区域在肌球蛋白连接的调节的参与模型进行了讨论。
Theo Wallimann and Andrew G. Szent-Gyorgyi* abstract: Specific antibodies directed against the regulatory light chains (R-LC) or essential light chains (SH-LC) of scallop myosin abolished calcium regulation in myofibrils, myosin, and heavy meromyosin by elevating the actin-activated Mg2+-ATPase activity in theabsence of calcium. Calcium dependence was completely eliminated at molar ratios of 2.5-3 antibodies bound per myosin. Monovalentanti-R-LC Fab and anti-SH-LC Fab fragments also desensitized myofibrils fully. High Ca2+-ATPase activity remained unaffected by the an-tibodies. Anti-SH-LC IgG reduced to about one-half the actin-activated Mg2+-ATPase in the presence of calcium and the potassium-activated ethylenediaminetetraacetic acid (EDTA)-ATPase activities. Anti-SH-LC Fab, however, de-sensitized without inhibiting the actin-activated Mg2+-ATPase. The desensitizing effect of both antibodies was abolished by prior absorption with the homologous myosin light chain. Calcium binding and R-LC content remained unaffected by anti-R-LC and anti-SH-LC IgG’s and by anti-SH-LC Fab. The anti-R-LC Fab fragment induced a significant (70%) dissociation of R-LC from myofibrils and myosins with con-comitant losses in calcium binding. In contrast, anti-R-LC IgG prevented the dissociation of R-LC frommyosin byEDTA. Binding of anti-R-LC IgG to myofibrils was proportional to their R-LC content. Increased amounts of anti-SH-LC IgG were bound by myofibrils devoid of R-LC. Bound anti-SH-LC antibody significantly inhibited the re-uptake of R-LC by EDTA-treated myofibrils as well as the full binding of anti-R-LC antibody. Certain rabbits produced a population of anti-SH-LC antibodies which were specific for this light chainand bound extensively to myosin but failed to desensitize it (nondesensitizing anti-SH-LC antibody). The desensitizing and nondesensitizing anti-SH-LC IgG popula-tions bound to different regions of the SH-LC on the myosin, and the binding of the two types of antibody to the SH-LC was nearly additive. The nondensitizing SH-antibody inhibited the reuptake of R-LC less, and its binding to myofibrils was not influenced by the absence of R-LC. These studies indicate a direct or indirect involvement of the SH-LC’s in myosin-linked regulation, raise the possibility of an interaction between the R-LC and SH-LC, and confirm the regulatory function of the scallop R-LC. A model for a relative location of the two types of light chains and the involvement of the sub-fragment-2 region of myosin in myosin linked regulation is discussed.