Department of Biochemistry and Molecular Biology, 600 Moye Blvd., Brody School of Medicine at East Carolina University, Greenville, NC 27834, USA.
Biochem Biophys Res Commun. 2011 Mar 4;406(1):74-8. doi: 10.1016/j.bbrc.2011.01.112. Epub 2011 Feb 3.
We examined the cardiomyopathy-causing tropomyosin mutations E180G, D175N, and V95A to determine their effects on actomyosin regulation. V95A reduced the ATPase rate when filaments were saturated with regulatory proteins both in the presence and absence of calcium, indicating either a stabilization of the inactive state or an inability to fully populate the active state. Effects of E180G and D175N were more complex. These two mutations increased ATPase rates at sub-saturating concentrations of troponin and tropomyosin as compared to wild type tropomyosin. At higher concentrations of regulatory proteins, ATPase rates became similar to wild type. Normal activation was achieved with the tight-binding myosin analog N-ethylmaleimide-S1, at saturating regulatory protein concentrations. These results suggest that the E180G and D175N mutations reduce the affinity of tropomyosin for actin and also destabilize troponin binding to the actin thin filaments.
我们研究了致心肌病的肌球蛋白调节轻链突变 E180G、D175N 和 V95A，以确定它们对肌球蛋白调节的影响。V95A 在有钙和无钙的情况下均使肌动球蛋白丝饱和时的 ATP 酶速率降低，表明要么是无活性状态的稳定化，要么是无法完全进入活性状态。E180G 和 D175N 的影响更为复杂。与野生型肌球蛋白轻链相比，这两种突变增加了肌钙蛋白和肌球蛋白调节蛋白亚饱和浓度时的 ATP 酶速率。在较高浓度的调节蛋白时，ATP 酶速率变得与野生型相似。在肌球蛋白类似物 N-乙基马来酰亚胺-S1 的紧密结合下，在饱和的调节蛋白浓度下实现了正常激活。这些结果表明，E180G 和 D175N 突变降低了肌球蛋白轻链与肌动蛋白的亲和力，并且还使肌钙蛋白与肌动蛋白细丝的结合不稳定。
