Allen P G, Shuster C B, Käs J, Chaponnier C, Janmey P A, Herman I M
Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Biochemistry. 1996 Nov 12;35(45):14062-9. doi: 10.1021/bi961326g.
Actin is a highly conserved protein in eukaryotes, yet different isoforms of this protein can be found within the same cell. To begin to explore whether isoactin sequence diversity leads to functional differences in actin filaments, we have examined the phalloidin binding kinetics and the bulk rheologic properties of purified actin isoforms from a variety of eukaryotic sources. We observe differences in the phalloidin association kinetics between muscle alpha- and cytoplasmic actins. Phalloidin dissociates from all mammalian actin isoforms tested at the same slow rate, while dissociation from yeast actin is 1 order of magnitude more rapid. The actin isoforms form viscoelastic gels to varying degrees with skeletal muscle alpha-actin gels being the most elastic, smooth muscle alpha- and gamma-actins being less elastic, and beta-actin not forming elastic structures under our experimental conditions. The sequence variation among isoforms is discussed in light of these biophysical and biochemical differences.
肌动蛋白是真核生物中一种高度保守的蛋白质，但在同一细胞内可以发现该蛋白质的不同亚型。为了探究肌动蛋白异构体序列多样性是否会导致肌动蛋白丝的功能差异，我们研究了来自多种真核生物来源的纯化肌动蛋白异构体的鬼笔环肽结合动力学和整体流变学性质。我们观察到肌肉α - 肌动蛋白和细胞质肌动蛋白之间在鬼笔环肽结合动力学上存在差异。鬼笔环肽以相同的缓慢速率从所有测试的哺乳动物肌动蛋白异构体上解离，而从酵母肌动蛋白上解离的速度快1个数量级。肌动蛋白异构体形成不同程度的粘弹性凝胶，其中骨骼肌α - 肌动蛋白凝胶弹性最大，平滑肌α - 和γ - 肌动蛋白弹性较小，而在我们的实验条件下β - 肌动蛋白不形成弹性结构。根据这些生物物理和生化差异对异构体之间的序列变异进行了讨论。
