α-原肌球蛋白中的两种肥厚型心肌病突变，即天冬氨酸175位突变为天冬酰胺（Asp175Asn）和谷氨酸180位突变为甘氨酸（Glu180Gly），对细肌丝运动Ca2⁺调节的影响。
Effects of two hypertrophic cardiomyopathy mutations in alpha-tropomyosin, Asp175Asn and Glu180Gly, on Ca2+ regulation of thin filament motility.
作者信息
Bing W, Redwood C S, Purcell I F, Esposito G, Watkins H, Marston S B
机构信息
Cardiac Medicine, Imperial College School of Medicine, National Heart and Lung Institute, London, United Kingdom.
出版信息
Biochem Biophys Res Commun. 1997 Jul 30;236(3):760-4. doi: 10.1006/bbrc.1997.7045.
The functional properties of wild type alpha-tropomyosin expressed in E. coli with an alanine-serine N-terminal leader (AS-alpha-Tm) were compared with those of AS-alpha-Tm with either of two missense mutations (Asp175Asn and Glu180Gly) shown to cause familial hypertrophic cardiomyopathy (FHC). Wild type AS-alpha-Tm and AS-alpha-Tm(Asp175Asn) binding to actin was indistinguishable from rabbit skeletal muscle ab-tropomyosin whilst the affinity of AS-alpha-Tm(Glu180Gly) was about threefold weaker. In vitro motility assays were performed with AS-alpha-tropomyosin incorporated into skeletal muscle actin-rhodamine phalloidin filaments moving over skeletal muscle heavy meromyosin. Under relaxing conditions (pCa9), troponin added to actin filaments containing AS-alpha-tropomyosin or mutant tropomyosins resulted in normal switch-off, with a decrease in the fraction filaments moving from >80% to <20%. Under activating conditions (pCa5), troponin had a minor effect upon actin-AS-alpha-tropomyosin filament velocity (increased by 5 +/- 1%, n=10), whereas the velocity increased by 18 +/- 3% (n=7) with actin filaments containing AS-alpha-tropomyosin(Asp175Asn) and by 21 +/- 2% (n=8) with filaments containing AS-alpha-tropomyosin(Glu180Gly) (p<0.05 compared with AS-alpha-tropomyosin). Thus FHC mutations in alpha-tropomyosin produce detectable changes in the Ca2+-regulation of thin filaments, presumably via altered interaction with troponin.
将在大肠杆菌中表达的带有丙氨酸 - 丝氨酸N端前导序列（AS-α-Tm）的野生型α - 原肌球蛋白的功能特性，与带有两种错义突变（Asp175Asn和Glu180Gly）之一的AS-α-Tm的功能特性进行了比较，这两种突变已被证明会导致家族性肥厚性心肌病（FHC）。野生型AS-α-Tm和AS-α-Tm（Asp175Asn）与肌动蛋白的结合与兔骨骼肌α - 原肌球蛋白无法区分，而AS-α-Tm（Glu180Gly）的亲和力约弱三倍。使用掺入骨骼肌肌动蛋白 - 罗丹明鬼笔环肽丝中的AS - α - 原肌球蛋白进行体外运动分析，该丝在骨骼肌重酶解肌球蛋白上移动。在松弛条件下（pCa9），向含有AS-α - 原肌球蛋白或突变原肌球蛋白的肌动蛋白丝中添加肌钙蛋白会导致正常的关闭，移动丝的比例从>80％降至<20％。在激活条件下（pCa5），肌钙蛋白对肌动蛋白 - AS-α - 原肌球蛋白丝速度的影响较小（增加5±1％，n = 10），而含有AS-α - 原肌球蛋白（Asp175Asn）的肌动蛋白丝速度增加18±3％（n = 7），含有AS-α - 原肌球蛋白（Glu180Gly）的丝速度增加21±2％（n = 8）（与AS-α - 原肌球蛋白相比，p<0.05）。因此，α - 原肌球蛋白中的FHC突变在细肌丝的Ca2 +调节中产生可检测到的变化，大概是通过与肌钙蛋白相互作用的改变。
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