THE DICTYOSTELIUM ESSENTIAL LIGHT CHAIN IS REQUIRED FOR MYOSIN FUNCTION
THE DICTYOSTELIUM ESSENTIAL LIGHT CHAIN IS REQUIRED FOR MYOSIN FUNCTION
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DOI：
10.1016/0092-8674(92)90614-i
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发表时间：
1992-06-12
期刊：
影响因子：
64.5
通讯作者：
CHISHOLM, RL
中科院分区：
文献类型：
--
作者：
POLLENZ, RS;CHEN, TLL;CHISHOLM, RL
通过反义RNA的过表达产生了表达低于野生型水平的0.5%的肌球蛋白必需轻链（EMLC）的网囊藻突变体（7-11）。来自7-11的细胞含有野生型水平的肌球蛋白重链（MHC）和调节轻链（RMLC）。从7-11细胞中分离的肌球蛋白由MHC和RMLC组成，以减少的化学计量比结合，并以ATP敏感的方式结合纯化的肌动蛋白。纯化的7-11肌球蛋白显示钙激活的ATP酶活性，V（max）约为野生型的15%-25%，ATP的K（m）为27 +/- 5 μ M，野生型为83 +/- 30 μ M。在肌动蛋白浓度高达17 μ M时，7-11肌球蛋白显示肌动蛋白激活的ATP酶活性大大降低。在表型上，7-11细胞类似于MHC突变体，在悬浮液中生长不良，并变得较大和多核。当饥饿的多细胞发育，7-11细胞需要几个小时比野生型细胞聚集。虽然多细胞聚集体最终形成，但它们无法进一步发展。细胞也不能响应于Con A处理而封端受体。由于表达EMLC的细胞在表型上与MHC无效突变体相似，因此EMLC似乎是肌球蛋白功能所必需的，至少部分是因为它是正常肌动蛋白激活的ATP酶活性所必需的。
A Dictyostelium mutant (7-11) that expresses less than 0.5% of wild-type levels of the myosin essential light chain (EMLC) has been created by overexpression of antisense RNA. Cells from 7-11 contain wild-type levels of the myosin heavy chain (MHC) and regulatory light chain (RMLC). Myosin isolated from 7-11 cells consists of the MHC with the RMLC associated in reduced stoichiometry, and binds to purified actin in an ATP-sensitive fashion. Purified 7-11 myosin displays calcium-activated ATPase activity with a V(max) about 15%-25% of that of wild type, and a K(m) for ATP of 27 +/- 5-mu-M versus 83 +/- 30-mu-M for wild type. At actin concentrations as high as 17-mu-M, 7-11 myosin displays greatly reduced actin-activated ATPase activity. Phenotypically, 7-11 cells resemble MHC mutants, growing poorly in suspension and becoming large and multinucleate. When starved for multicellular development, 7-11 cells take several hours longer than wild-type cells to aggregate. Although multicellular aggregates eventually form, they fail to develop further. The cells are also unable to cap receptors in response to Con A treatment. Since cells expressing the EMLC are phenotypically similar to MHC null mutants, the EMLC appears necessary for myosin function, at least in part because it is required for normal actin-activated ATPase activity.