Expression of Nonmuscle Myosin Heavy and Light Chains in Smooth Muscle

Document Type




Format of Original

8 p.

Publication Date



American Physiological Society

Source Publication

American Journal of Physiology - Cell Physiology

Source ISSN


Original Item ID

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.


American Journal of Physiology - Cell Physiology, Vol. 257, No. 5 (November 1989): C997-C1004. DOI.

Thomas Eddinger was affiliated with the University of Virginia School of Medicine at the time of publication.