Asami Y, Funatsu T, Ishiwata S
Department of Physics, School of Science and Engineering, Waseda University, Tokyo.
J Biochem. 1988 Jan;103(1):72-5. doi: 10.1093/oxfordjournals.jbchem.a122241.
We examined by means of the immunoblotting technique the transition of beta-actinin isoforms during the development of the chicken from 5 day embryo to adult. As an antigen, beta-actinin was prepared from adult chicken breast muscle (pectoralis major) and polyclonal antibody was obtained by injecting undenatured beta-actinin into a rabbit. Immunoblotting examination of breast muscle at several stages of development (except 5 day embryo, in which the whole body minus the head and limbs was examined) showed that the species of beta-actinin subunits change during development: 1) beta I is already present in 5 day embryo, whereas beta II appears only after 9 days. 2) In 5 day embryo, we found, instead of beta II, a new subunit (designated beta III) that cross-reacts with the antibody, has the apparent molecular weight of 30,000 daltons and has a slightly alkaline isoelectric point compared with beta I. The content of beta III gradually decreased and beta III completely disappeared a week after hatching. Such a type of transition of the isoforms in beta-actinin subunits is similar to that observed in other muscle proteins. The transition of beta-actinin isoforms may correlate to the organization of an I-Z-I brush, especially to the length determination of thin filaments, because the developmental stage at which beta III disappears coincides with that at which the length of thin filaments is strictly determined.
我们运用免疫印迹技术研究了从5日龄胚胎到成年鸡发育过程中β - 辅肌动蛋白亚型的转变。以成年鸡胸肌（胸大肌）制备β - 辅肌动蛋白作为抗原，并将未变性的β - 辅肌动蛋白注射到兔子体内获得多克隆抗体。对发育几个阶段的胸肌进行免疫印迹检测（5日龄胚胎除外，检测的是去除头部和四肢后的整体），结果显示β - 辅肌动蛋白亚基种类在发育过程中发生变化：1）βI在5日龄胚胎中就已存在，而βII直到9日龄后才出现。2）在5日龄胚胎中，我们发现了一种新的亚基（命名为βIII），它与抗体发生交叉反应，表观分子量为30,000道尔顿，与βI相比，其等电点略呈碱性。βIII的含量逐渐降低，在孵化一周后βIII完全消失。β - 辅肌动蛋白亚基中这种亚型的转变与在其他肌肉蛋白中观察到的类似。β - 辅肌动蛋白亚型的转变可能与I - Z - I 刷毛的组织有关，特别是与细肌丝长度的确定有关，因为βIII消失的发育阶段与细肌丝长度被严格确定的阶段相吻合。
