Gaylinn B D, Eddinger T J, Martino P A, Monical P L, Hunt D F, Murphy R A
Department of Physiology, University of Virginia School of Medicine, Charlottesville 22908.
Am J Physiol. 1989 Nov;257(5 Pt 1):C997-1004. doi: 10.1152/ajpcell.1989.257.5.C997.
We have compiled evidence that nonmuscle isoforms of both myosin heavy chain (NM MHC) and myosin regulatory light chain (NM LC20) are present in fully differentiated smooth muscles (SM). In swine carotid media sodium dodecyl sulfate-gel electrophoresis separated three MHC bands. The upper two bands were identified by immunoblotting as SM-specific isoforms. The lowest MHC band amounted to 14 +/- 2% of the total MHC and was electrophoretically and antigenically similar to platelet MHC. Two-dimensional gel electrophoresis of swine carotid media extracts resolved multiple LC20 species, including phosphorylated and "satellite" forms. Mass spectrometric analysis of tryptic peptides from blots of these gels demonstrated two LC20 isoforms. The measured peptide masses correspond with two published cDNA sequences proposed to represent SM and NM LC20 isoforms. These sequences readily explain the electrophoretic behavior of the isoforms. The minor isoform's abundance (16 +/- 3%, corresponding to NM MHC), antigenic properties, and pattern of expression in tissue culture all confirm that this is a NM LC20 isoform. The localization and functional significance of NM myosin in smooth muscle is unknown.
我们已收集到证据表明，肌球蛋白重链（NM MHC）和肌球蛋白调节轻链（NM LC20）的非肌肉同工型存在于完全分化的平滑肌（SM）中。在猪颈动脉中膜，十二烷基硫酸钠凝胶电泳分离出三条MHC条带。通过免疫印迹法鉴定，上面两条条带为平滑肌特异性同工型。最低的MHC条带占总MHC的14±2%，在电泳和抗原性上与血小板MHC相似。猪颈动脉中膜提取物的二维凝胶电泳解析出多种LC20种类，包括磷酸化形式和“卫星”形式。对这些凝胶印迹上胰蛋白酶肽段的质谱分析显示有两种LC20同工型。测得的肽质量与两个已发表的cDNA序列相符，这两个序列被认为分别代表平滑肌和非肌肉LC20同工型。这些序列很容易解释同工型的电泳行为。次要同工型的丰度（16±3%，对应于NM MHC）、抗原特性以及在组织培养中的表达模式均证实这是一种NM LC20同工型。非肌肉肌球蛋白在平滑肌中的定位和功能意义尚不清楚。
