Smooth muscle myosin heavy chains combine to form three native myosin isoforms

1993 ◽  
Vol 264 (5) ◽  
pp. H1653-H1662 ◽  
Author(s):  
A. E. Tsao ◽  
T. J. Eddinger
Keyword(s):  
Smooth Muscle ◽  
Sodium Dodecyl ◽  
Coiled Coil ◽  
Smooth Muscle Myosin ◽  
Polyacrylamide Gel ◽  
Myosin Isoforms ◽  
Myosin Heavy Chains ◽  
Polyacrylamide Gels ◽  
Heavy Chains ◽  
Muscle Myosin

Two smooth muscle myosin heavy chains (MHC; SM1 and SM2) of approximately 204 and 200 kDa exist in smooth muscle cells and can be visualized on reducing sodium dodecyl sulfate (SDS)-polyacrylamide gels. Chymotryptic digestion of the native myosin molecule results in two fragments: heavy meromyosin (HMM) and light meromyosin (LMM). LMM is the alpha-helical coiled-coil carboxy terminal half of the molecule containing the difference peptide between SM1 and SM2. Electrophoresis of the LMM fragments on a reducing SDS-polyacrylamide gel resolves two subunits from the two MHC [LM1 from SM1 (approximately 100 kDa) and LM2 from SM2 (approximately 95 kDa), where LM1 and LM2 are LMM from SM1 and SM2, respectively]. CuCl2 oxidation of the LMM fragment forms intramolecular disulfide bonds between adjacent cysteines on the two LMM fragments. When the native LMM is oxidized with CuCl2 and run on a nonreducing SDS-polyacrylamide gel, three bands are observed, which migrate at approximately 195, 190, and 185 kDa (bands 1, 2, and 3). Excision of these bands and electrophoresis on a reducing SDS-polyacrylamide gel show their subunit composition. Band 1 is composed solely of LM1. Band 2 is composed of an equal ratio of LM1 and LM2, and band 3 is composed solely of LM2. Using a variety of biochemical procedures, along with nonreducing SDS-polyacrylamide gels, we interpret these results to indicate that there are three smooth muscle myosin isoforms that result from the various combinations of the two smooth muscle MHC (SM1 homodimer, SM1-SM2 heterodimer, and SM2 homodimer).

scholarly journals The Heavy-chain Stoichiometry of Smooth Muscle Myosin is a Characteristic of Smooth Muscle Tissues

1988 ◽  
Vol 41 (4) ◽  
pp. 409 ◽  
Author(s):  
Mukhallad A Mohammad ◽  
Malcolm P Sparrow
Keyword(s):  
Smooth Muscle ◽  
Heavy Chain ◽  
Relative Proportion ◽  
Sodium Dodecyl ◽  
Smooth Muscle Myosin ◽  
Human Bronchus ◽  
Heavy Chains ◽  
Tissue Extracts ◽  
Muscle Tissues ◽  
Muscle Myosin

The stoichiometry of the two heavy chains of myosin in smooth muscle was determined by electrophoresing extracts of native myosin and of dissociated myosin on sodium dodecyl sulfate (SDS) 4%-polyacrylamide gels. The slower migrating heavy chain was 3�6 times more abundant in toad stomach, 2�3 in rabbit myometrium, 2�0 in rat femoral artery, 1�3 in guinea pig ileum, 0�93 in pig trachea and 0�69 in human bronchus, than the more rapidly migrating chain. Both heavy chains were identified as smooth muscle myosin by immunoblotting using antibodies to smooth muscle and nonmuscle myosin. The unequal proportion of heavy chains suggested the possibility of native isoforms of myosin comprised of heavy-chain homodimers. To test this, native myosin extracts were electrophoresed on non-dissociating (pyrophosphate) gels. When each band was individually analysed on SDS-polyacrylamide gel the slowest was found to be filamin and the other bands were myosin in which the relative proportion of the heavy chains was unchanged from that found in the original tissue extracts. Since this is incompatible with either a heterodimeric or a homodimeric arrangement it suggests that pyrophosphate gel electrophoresis is incapable of separating putative isoforms of native myosin.

Phosphorylation of vertebrate nonmuscle and smooth muscle myosin heavy chains and light chains

1993 ◽  
Vol 127-128 (1) ◽  
pp. 219-227 ◽  
Author(s):  
Robabeh S. Moussavi ◽  
Christine A. Kelley ◽  
Robert S. Adelstein
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Myosin ◽  
Light Chains ◽  
Myosin Heavy Chains ◽  
Heavy Chains ◽  
Muscle Myosin

Two smooth muscle myosin heavy chains differ in their light meromyosin fragment

Biochemistry ◽  
1988 ◽  
Vol 27 (10) ◽  
pp. 3807-3811 ◽  
Author(s):  
Thomas J. Eddinger ◽  
Richard A. Murphy
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Myosin ◽  
Myosin Heavy Chains ◽  
Heavy Chains ◽  
Muscle Myosin

SMOOTH MUSCLE MYOSIN HEAVY CHAINS ARE DEVELOPMENTALLY REGULATED IN THE RABBIT BLADDER

2000 ◽  
Vol 164 (4) ◽  
pp. 1376-1380 ◽  
Author(s):  
VICTOR K. LIN ◽  
JAMES B. ROBERTSON ◽  
I-LING LEE ◽  
PHILIPPE E. ZIMMERN ◽  
JOHN D. McCONNELL
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Myosin ◽  
Myosin Heavy Chains ◽  
Developmentally Regulated ◽  
Heavy Chains ◽  
Rabbit Bladder ◽  
Muscle Myosin

Two different heavy chains are found in smooth muscle myosin

1986 ◽  
Vol 250 (6) ◽  
pp. C861-C870 ◽  
Author(s):  
A. S. Rovner ◽  
M. M. Thompson ◽  
R. A. Murphy
Keyword(s):  
Smooth Muscle ◽  
Sodium Dodecyl Sulfate ◽  
Heavy Chain ◽  
Sodium Dodecyl ◽  
Smooth Muscles ◽  
Protein Band ◽  
Smooth Muscle Myosin ◽  
Heavy Chains ◽  
Dodecyl Sulfate ◽  
Muscle Myosin

Two putative myosin heavy chains designated SM1 and SM2 were detected on a 3.5% polyacrylamide-sodium dodecyl sulfate gel electrophoresis system loaded with homogenates of several mammalian smooth muscles. The two polypeptides were present in nearly equal amounts in all smooth muscle tissues tested and in myosin purified from swine carotid media and stomach. Both proteins were equally stained by smooth muscle-specific myosin antibodies. The smaller of the polypeptides had a mobility nearly identical to that of the single heavy chain observed in purified fast-twitch skeletal myosin. Electrophoresis of pyrophosphate extracts from swine carotid media, swine stomach, rabbit thoracic aorta, and guinea pig taenia coli on nondenaturing pyrophosphate gels revealed a single protein band. When subsequently electrophoresed on a sodium dodecyl sulfate gel, the native bands from swine tissue extracts revealed the two putative heavy chains in nearly equal amounts, as well as a large amount of a higher molecular weight peptide whose properties reflect those of filamen. Sodium dodecyl sulfate gel analysis of the myosin band from pyrophosphate gels of purified swine stomach myosin showed exclusively the two heavy chains in a nearly 1:1 ratio. Smooth muscle myosin migrates homogeneously on pyrophosphate gels, and the virtual equality of the two heavy chains may reflect the presence of large amounts of a myosin isoenzyme, which is a heavy-chain heterodimer.

scholarly journals The carboxyl-terminal isoforms of smooth muscle myosin heavy chain determine thick filament assembly properties

2002 ◽  
Vol 156 (1) ◽  
pp. 113-124 ◽  
Author(s):  
Arthur S. Rovner ◽  
Patricia M. Fagnant ◽  
Susan Lowey ◽  
Kathleen M. Trybus
Keyword(s):  
Smooth Muscle ◽  
Thick Filament ◽  
Smooth Muscle Myosin ◽  
Myosin Isoforms ◽  
Heavy Chains ◽  
Filament Assembly ◽  
Filament Structure ◽  
Alternatively Spliced ◽  
Muscle Myosin

The alternatively spliced SM1 and SM2 smooth muscle myosin heavy chains differ at their respective carboxyl termini by 43 versus 9 unique amino acids. To determine whether these tailpieces affect filament assembly, SM1 and SM2 myosins, the rod region of these myosin isoforms, and a rod with no tailpiece (tailless), were expressed in Sf 9 cells. Paracrystals formed from SM1 and SM2 rod fragments showed different modes of molecular packing, indicating that the tailpieces can influence filament structure. The SM2 rod was less able to assemble into stable filaments than either SM1 or the tailless rods. Expressed full-length SM1 and SM2 myosins showed solubility differences comparable to the rods, establishing the validity of the latter as a model for filament assembly. Formation of homodimers of SM1 and SM2 rods was favored over the heterodimer in cells coinfected with both viruses, compared with mixtures of the two heavy chains renatured in vitro. These results demonstrate for the first time that the smooth muscle myosin tailpieces differentially affect filament assembly, and suggest that homogeneous thick filaments containing SM1 or SM2 myosin could serve distinct functions within smooth muscle cells.

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