Studies on the myosin molecule from smooth muscle

Abstract

SynopsisThe myosin molecule was extracted from the smooth muscle parts of horse esophagus and purified by ammonium sulfate fractionation. The schlieren pattern of the sedimentation velocity run showed a very sharp single peak of 5.9 S (~2 0 ,~) . Molecular weight of the protein was measured by means of the Archibald and sedimentation equilibrium methods, both in 0.5M KCl buffered by 1/150M phosphate at pH 7.5 and a t 5°C. The values obtained were 6.25 X 105 and 5.81 X lo5, respectively, for the two methods. The second virial coefficients were 1.1 X lo4 and 1.2 X ml/g. Denatured smooth muscle myosin was prepared in a solution of 5M guanidine HC1 containing 0.4M KCI and 0.2M @-mercaptoethanol buffered at pH 8.0. The weight-average molecular weight of the denatured smooth muscle myosin was 2.24 X lo5 and the second virial coefficient was 7.6 X lo-' ml/g. The values described above are in good agreement with those reported for rabbit skeletal myosin with ammonium sulfate fractionation. The molecular dimension of the molecule is estimated as the value for an axial ratio of 100, assuming a rigid rod molecular model for this molecule, both the thermodynamical and hydrodynamical treatment being in a good agreement with this estimation.Molecular weight measurements of the myosin molecule have been performed extensively on myosin from rabbit skeletal muscle. The reported values of the molecular weight range between 4.2 X lo5 and 6.2 x 106.These discrepancies in the values of the molecular weight of myosin were discussed from the viewpoints of refractive index increment of the solution,l the method of the molecular weight measurement12 and the nature of the protein preparati~ns.~ Nevertheless, the molecular weight of rabbit myosin, the most essential property of the molecule, is still a subject of controversy.On the other hand, the physiological difference in the mode of the muscle contraction between the skeletal and the smooth muscle is known to be quite significant.

Extractability and properties of the contractile proteins of vertebrate smooth muscle

“…Myosin has been isolated from several vertebrate smooth muscles: cow carotid (Hamoir & Laszt 1962 b ; Huriaux, Pechere & Hamoir 1965), chicken gizzard (Barany, Barany, Gaetjens & Bailin 1966), horse oesophagus (Kotera, Yokoyama Yamaguchi & Miyazawa 1969;Yamaguchi, Miyazawa & Sekine 1970), rabbit uterus (Needham & Williams 1963c;Wachsberger & Kaldor 1971) and human uterus (Groschel-Stewart 1971). All physicochemical determinations carried out on these myosins suggest that their size and gross shape are similar to those of the skeletal and cardiac myosins.…”

A Study of the Mechanism of Contraction in Vertebrate Smooth Muscle

“…One must also consider, as Hamoir does, that in vivo and unaffected by the operations of isolation this actomyosin, sometimes called tonoactomyosin, may indeed be more soluble, and relate this to the lability of the myosin in the intact cell discussed in this review. Kotera, Yokoyama, Yamaguchi & Miyazawa (1969) give the molecular weight of oesophageal myosin, by two different methods, as 5-81 x 105 and 6.25 give I 560 A for the length of the myosin rod from gizzard myosinslightly longer than that from chicken-breast myosin (Cohen et al, 1970) histidine content is definitely lower, aspartic and glutamic acids are usually raised and lysine lowered. The negative net charge is probably higher at neutral pH than that of the skeletal muscle protein.…”

Physical properties of myosin from aortic smooth muscle

“…Although reviewers have usually accepted the physical properties of smooth muscle myosins as similar to those of skeletal muscle myosin (Hartshorne & Askoy, 1977;Hamoir, 1973), others have pointed out that comparatively little is known about smooth muscle contractile proteins (Pollard & Weihing, 1974). The sedimentation coefficient has been determined for bovine carotid myosin (Hamoir & Laszt, 1962), lapine uterus myosin (Cohen et al, 1961;Wachsberger & Kaldor, 1971), gizzard myosin (Barany et al, 1966), and equine esophagus myosin (Kotera et al, 1969). With the exception of one of the uterine myosin reports (Wachsberger & Kaldor, 1971), these values have been consistently and significantly lower than that of skeletal muscle myosin.…”