Janmey P A, Hvidt S, Oster G F, Lamb J, Stossel T P, Hartwig J H
Hematology Unit, Massachusetts General Hospital, Boston.
Nature. 1990 Sep 6;347(6288):95-9. doi: 10.1038/347095a0.
Actin is an adenine nucleotide-binding protein and an ATPase. The bound adenine nucleotide stabilizes the protein against denaturation and the ATPase activity, although not required for actin polymerization, affects the kinetics of this assembly Here we provide evidence for another effect of adenine nucleotides. We find that actin filaments made from ATP-containing monomers, the ATPase activity of which hydrolyses ATP to ADP following polymerization, are stiff rods, whereas filaments prepared from ADP-monomers are flexible. ATP exchanges with ADP in such filaments and stiffens them. Because both kinds of actin filaments contain mainly ADP, we suggest the alignment of actin monomers in filaments that have bound and hydrolysed ATP traps them conformationally and stores elastic energy. This energy would be available for release by actin-binding proteins that transduce force or sever actin filaments. These data support earlier proposals that actin is not merely a passive cable, but has an active mechanochemical role in cell function.
肌动蛋白是一种腺嘌呤核苷酸结合蛋白，也是一种ATP酶。结合的腺嘌呤核苷酸可稳定蛋白质使其不易变性，ATP酶活性虽不是肌动蛋白聚合所必需的，但会影响其组装动力学。在此，我们提供了腺嘌呤核苷酸另一种作用的证据。我们发现，由含ATP的单体形成的肌动蛋白丝，其ATP酶活性在聚合后将ATP水解为ADP，这种肌动蛋白丝是硬棒状的，而由ADP单体制备的丝则是柔性的。ATP在这种丝中与ADP交换并使其变硬。由于这两种肌动蛋白丝主要都含有ADP，我们认为，在已结合并水解ATP的丝中肌动蛋白单体的排列在构象上限制了它们，并储存了弹性能量。这种能量可由转导力或切断肌动蛋白丝的肌动蛋白结合蛋白释放出来。这些数据支持了早期的观点，即肌动蛋白不仅仅是一种被动的缆绳，而是在细胞功能中具有积极的机械化学作用。
