ELECTRON-MICROSCOPY OF SYNTHETIC MYOSIN-FILAMENTS - EVIDENCE FOR CROSS-BRIDGE FLEXIBILITY AND COPOLYMER FORMATION
ELECTRON-MICROSCOPY OF SYNTHETIC MYOSIN-FILAMENTS - EVIDENCE FOR CROSS-BRIDGE FLEXIBILITY AND COPOLYMER FORMATION
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DOI：
10.1083/jcb.67.1.93
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发表时间：
1975-01-01
影响因子：
7.8
通讯作者：
POLLARD, TD
中科院分区：
文献类型：
--
作者：
POLLARD, TD
Electron micrographs of negatively stained synthetic myosin filaments reveal that surface projections, believed to be the heads of the constituent myosin molecules, can exist in two configurations. Some filaments have the projections disposed close to the filament backbone. Other filaments have all of their projections widely spread, tethered to the backbone by slender threads. Filaments formed from the myosins of skeletal muscle, smooth muscle, and platelets each have distinctive features, particularly their lengths. Soluble mixtures of skeletal muscle myosin with either smooth muscle myosin or platelet myosin were dialyzed against 0.1 M KCI at pH 7 to determine whether the simultaneous presence of two types of myosin would influence the properties of the filaments formed. In every case, a single population of filaments formed from the mixtures. The resulting filaments are thought to be copolymers of the two types of myosin, for several reasons:(a) their length-frequency distribution is unimodal and differs from that predicted for a simple mixture of two types of myosin filaments;(b) their mean length is intermediate between the mean lengths of the filaments formed separately from the two myosins in the mixture;(c) each of the filaments has structural features characteristic of both of the myosins in the mixture; and (d) their size and shape are determined by the proportion of the two myosins in the mixture.Myosins from skeletal muscle,(6, 10), smooth muscle (4, 9), and several non-muscle cells (1, 2, 3, 16, 17, 18, 24, 26) spontaneously assemble into bipolar filaments when placed in buffers approximating physiological conditions. All of these" synthetic" myosin filaments have certain features in common, but filaments of each type of myosin have distinctive sizes and shapes. Skeletal muscle myosin filaments are large, smooth muscle myosin filaments are intermediate in size, and most cytoplasmic myosin filaments are very small. These differences in size make it possible to test whether different myosins can copolymerize.
