TROPOMYOSIN - CRYSTAL STRUCTURE POLYMORPHISM AND MOLECULAR INTERACTIONS
TROPOMYOSIN - CRYSTAL STRUCTURE POLYMORPHISM AND MOLECULAR INTERACTIONS
复制标题
DOI：
10.1016/0022-2836(69)90128-4
复制
发表时间：
1969-01-01
影响因子：
5.6
通讯作者：
LONGLEY, W
中科院分区：
文献类型：
--
作者：
CASPAR, DLD;COHEN, C;LONGLEY, W
α蛋白原肌球蛋白形成多种有序聚集体。真正的晶体具有非常开放的晶格和至少两个其他网络形式产生的等电点附近与纤维聚集体一起。三种不同类型的tactoids的轴向周期约400欧姆形成的二价阳离子。对多晶型的电子显微镜观察与对晶格和用镁产生的tactoids的X-射线衍射测量有关。晶体的一个投影的X-射线图案已从由与电子显微镜照片雅阁排列的棒状分子组成的模型以低分辨率解释。晶体中的原肌球蛋白分子在极性细丝中首尾相连，周期为400 nm。在400 μ m的轴向周期中，纤维在相隔约230 μ m和170 μ m的两个位点上交叉连接，使纤维发生周期性弯曲.本研究的主要结论是：原肌球蛋白分子存在一种特殊的极性端-端键，这决定了在多形网和类触体中观察到的约400 μ m的轴向周期;有两个交叉连接位点参与网状结构的形成;在许多形式中，极性细丝以相反方向成对排列;分子卷曲螺旋通常在极性细丝中超螺旋。肌肉I带的周期性可以用原肌球蛋白端对端结合的400碱基重复特征来识别。这种多态性可能与原肌球蛋白的结构和调节功能有关。
The α-protein tropomyosin forms a variety of ordered aggregates. True crystals with a very open lattice and at least two other net forms are produced near the isoelectric point together with fibrous aggregates. Three distinctive types of tactoids with axial periodicities about 400 Å are formed with divalent cations. The electron microscope observations on the polymorphic forms have been related to X-ray diffraction measurements on the crystal lattice and the tactoids produced with magnesium.The X-ray pattern of one projection of the crystal has been interpreted at low resolution from a model composed of rod-shaped molecules arranged in accord with the electron micrographs. The tropomyosin molecules in the crystal are associated head-to-tail in polar filaments with a 400 Å period. The filaments are periodically bent as a consequence of the cross connections at two sites alternatively separated by about 230 Å and 170 Å in the 400 Å axial period.The principal conclusions of this study are: there is a specific polar end-to-end bonding of tropomyosin molecules which defines the period of about 400 Å observed in the polymorphic nets and tactoids; there are two cross-connecting sites which are involved in net formation; in many of the forms, the polar filaments are arranged in oppositely directed pairs; the molecular coiled-coil is often supercoiled in the polar filaments. The periodicity in the I band of muscle can be identified with the 400 Å repeat characteristic of the end-to-end association of tropomyosin. The polymorphism observedin vitromay be related to the structural and regulatory functions of tropomyosin in muscle.