Regulatory Factor of Smooth Muscle Contraction: Relation of Leiotonin with Myosin Light Chain Kinase

提出了一种制备青藤碱的新方法。人们偶然发现，二甲基亚砜（DMSO）是一种非常有用的蛋白质分级试剂，不仅用于上述目的，而且用于一般目的。用DMSO从鸡砂囊和牛胃中未经特殊处理获得了一种表现出比肌球蛋白轻链激酶（MLCK）活性大得多的肌动球蛋白激活活性或平滑肌肽活性的级分（L/K > 100，取0.1M提取物的L/K为1）。使用特殊的程序，可以获得MLCK活性（L/K > 3，000）的制备空隙。结果表明，该酶的主要活性组分是一个分子量为155 kDa的蛋白质，与MLCK分子量无明显区别;胰蛋白酶在特定条件下产生的一个片段也具有一定的活性，但不具有MLCK活性。这可能对应于leiotonin的旧制剂。负责leiotonin活性（和/或MLCK活性）的155 kDa组分的一级序列已被确定为从C-末端到120 kDa。作为一个整体，平滑肌调节由leiotonin介导的想法已被进一步证实。

A new method of preparing leiotonin was developed. It was incidentally found that dimethyl sulfoxide (DMSO) is a very useful agent for protein fractionation, not only for the above purpose but also for general ones. Using DMSO, a fraction exhibiting much larger actomyosin-activating activity, or leiotonin activity, than myosin light chain kinase (MLCK) activity (L/K > 100, taking L/K of 0.1 M extract as 1) was obtained both from chicken gizzard and boving stomach without particular treatment. Using special procedures, a preparation void of MLCK avtivity (L/K > 3,000) could be obtained. The component responsibe for the leiotonin activity was a protein of 155 kDa, indistinguishable from MLCK in its molecular weight.A fragment produced by trypsin under specified conditions exhibited also a definite leiotonin activity without MLCK activity. This may correspond to the old preparation of leiotonin.The primary sequence of the 155 kDa component responsible for leiotonin activity (and/or MLCK activity) has been determined up to 120 kDa from the C- terminal.As a whole the idea that smooth muscle regulation is mediated by leiotonin has further been substantiated.