Variations in the small subunits of different myosins

Locker, R.H.; Hagyard, C.J.

doi:10.1016/0003-9861(67)90230-5

Cited by 38 publications

(9 citation statements)

References 3 publications

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“…The activation of actomyosin ATPase by tropomyosin appears to be restricted to Limulus myosin, and it is not known which particular feature of the Limulus myosin molecule could account for this effect. The most variable features of different myosins are their light chains (Locker and Hagyard, 1967;Samaha et al, 1970;Lowey and Risby, 1971;Sarkar et al, 1971). The light chains of Limulus myosin are different from those of rabbit ( Fig.…”

Section: Discussionmentioning

confidence: 99%

Activation of the Adenosine Triphosphatase of Limulus polyphemus Actomyosin by Tropomyosin

Lehman

Szent‐Györgyi

1972

The Journal of General Physiology

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Purified actin does not stimulate the adenosine triphosphatase (ATPase) activity of Limulus myosin greatly. The ATPase activity of such reconstituted preparations is only about one-fourth the ATPase of myofibrils or of natural actomyosin. Actin preparations containing tropomyosin, however, activate Limulus myosin fully. Both the tropomyosin and the actin preparations appear to be pure when tested by different techniques. Tropomyosin combines with actin but not with myosin and full activation is reached at a tropomyosin-to-actin ratio likely to be present in muscle. Tropomyosin and actin of several different animals stimulate the ATPase of Limulus myosin. Tropomyosin, however, is not required for the ATPases of scallop and rabbit myosin which are fully activated by pure actin alone. Evidence is presented that Limulus myosin, in the presence of ATP at low ionic strength, has a higher affinity for actin modified by tropomyosin than for pure actin.

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Section: Discussionmentioning

confidence: 99%

Activation of the Adenosine Triphosphatase of Limulus polyphemus Actomyosin by Tropomyosin

Lehman

Szent‐Györgyi

1972

The Journal of General Physiology

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“…Finally, the slowest of the RM bands, hitherto referred to as LCQa, will be called LC1R. (15)(16)(17). Although the mobilities of some components in the WM pattern were found to be similar to those of components in RM and CM, no definitive conclusion could be reached as to whether they were identical.…”

Section: Electrophoresis Of Mixed Samples Of Rm Wm and CMmentioning

confidence: 99%

“…On the other hand, CM and RM are similar with respect to these parameters (12)(13)(14). Several reports indicate that these similarities and differences are also reflected in the light-chain patterns (15)(16)(17). There is, however, considerable disagree- ment among these reports.…”

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confidence: 99%

“…There is, however, considerable disagree- ment among these reports. The number of electrophoretically distinguishable light-chain components present in myosin preparations from different types of muscle in various species ranges from one to six (2,(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). Estimated molecular weights fall in the range of 15,000-30,000 (3,5,15,16,19,20,(23)(24)(25)(26)(27)(28).…”

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confidence: 99%

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Light Chains of Myosins from White, Red, and Cardiac Muscles

Sarkar¹,

Sreter

Gergely³

1971

Proc. Natl. Acad. Sci. U.S.A.

201

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Purified preparations of rabbit skeletal white, red, and cardiac muscle myosin (WM, RM, and CM) were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Significant differences in both the molecular weights and number of light chains in these myosins were found. WM has three distinct light-chain components (LCiw, LC2W, LC3W) having molecular weights of 25,500, 17,400, and 15,100, respectively (29), extensively used for the separation of various proteins and the determination of their molecular weights, we decided to apply this method to a reinvestigation of the light chains of rabbit WM, RM, and CM. Our results clearly show that both quantitative and qualitative differences exist between light chains in the different types of muscle; these will be discussed in terms of the isozymic nature of myosin. MATERIALS AND METHODS Preparation of myosinRabbit soleus, semitendinosus, crureus, and intertransversarius (red muscles); the outer layers of vastus lateralis and adductor magnus (white muscles); and heart ventricle (cardiac muscle) were used for the preparation of myosin (8). Myosin was further purified by column chromatography on DEAE-Sephadex A-50, essentially by the methods of Richards et al. (30). 150-200 mg of myosin, dissolved in a solution containing 0.04 M Na4P207 (pH 7.5), 0.1 mM EDTA, and 0.1 mM dithiothreitol (buffer I), were applied to a column (2.5 X 35 cm) of DEAE-Sephadex A-50 equilibrated with the same buffer. The column was then washed with 2-3 column volumes of buffer I. Under these conditions myosin remained on the column, but other proteins (5-10% of the input) were eluted. A linear gradient of 0-0.5 AI NaCl in buffer I was then applied. Myosin was eluted as a sharp single peak at 0.13-0.15 M NaCl and concentrated by precipitation either at low ionic strength after dilution or with (NH4)2SO4 at 50% saturation. Myosin was finally dissolved in a solution containing 0.01 M sodium phosphate (pH 7.0), 0.5 M NaCl, 0.1 mM EDTA, and 0.1 mM dithiothreitol (buffer II). For the determination of ATPase activities of column-purified myosin, K4P207 and KCl were used in the elution buffers for chromatography and myosin was finally dissolved in a solution containing 0.5 M KCl, 1 mM EDTA, and 10 mM Ntris(hydroxymethyl) methyl-2-aminoethane sulfonic acid (TES), pH 7.0.Typical

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“…Myosin components which might change under these circumstances include both the light and heavy chains. Myosin light chains are distinctive for different types of muscle (28)(29)(30)(31) and may function to modify enzyme activity (32)(33)(34). It has recently been demonstrated that by exchanging light chains of red and white muscle myosin the specific activities of the reconstituted myosins were similar to the specific activity of the myosin from which the subunits arose (35).…”

Section: Rovetto Hjalmarson Morgan Barrett Goldsteinmentioning

confidence: 98%

Hormonal Control of Cardiac Myosin Adenosine Triphosphatase in the Rat

Rovetto

Hjalmarson

Morgan

et al. 1972

Circulation Research

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Cardiac function was impaired in hearts from hypophysectomized rats. Corresponding to the decrease in performance, myosin from the hearts of these rats exhibited a decreased Ca 2 + -activated ATPase activity. Myosin ATPase activated by K + or NH 4 + was not different in any of the preparations studied. The decreased Ca 2 + -activated ATPase was observed in cardiac myosin but not in red or white skeletal muscle myosin. Treatment with thyroxine, but not with growth hormone, restored cardiac myosin ATPase and performance to normal. Hypothyroidism produced a decrease in cardiac myosin ATPase activity comparable to that seen after hypophysectomy, suggesting that the absence of thyroid hormone was responsible for the alterations. However, hyperthyroidism did not increase ATPase activity above normal values. Adrenalectomy failed to alter myosin ATPase. Anion exchange chromatogTaphy of the myosins and addition of various concentrations of Na + , Ca 2 + , and Mg 2+ did not abolish the differences in myosin ATPase. The results strongly suggest that the lower myosin ATPase activity in the absence of thyroid hormone was the result of a change in the myosin molecule per se and that the lower enzymatic activity was involved in the lower cardiac performance in these rats. KEY WORDS hyperthyroidismcardiac function thyroid hormone hypothyroidism adrenal insufficiency skeletal muscle myosin • Several recent studies have shown an alteration in the enzymatic activity of myosin from hearts of animals in abnormal hormonal states. A decrease was found in ATPase activities of myofibrils, actomyosin, and myosin from adrenalectomized cats (1) that correlated with cardiac function (2). An increase in myosin ATPase activity was noted in hyperthyroid guinea pigs (3). In a preliminary report of the present work, we reported that decreased ventricular function and decreased ATPase activity of myosin were found in hearts of hypophysectomized rats (4).function and myosin ATPase in hypophysectomized rats, (2) to identify the hormone involved in this abnormal state, and (3) to try various assay conditions and modifications of myosin which might normalize the apparent low specific enzymatic activity of cardiac myosin from hypophysectomized animals. Methods ANIMAL TECHNIQUESNormal, hypophysectomized (hypox) or adrenalectomized (adrenex) male Sprague-Dawley rats were used. The adrenex rats were given 0.9* saline to drink but otherwise only routine care and feeding was given to the rats.Thyroxine, growth hormone, and propylthiouracil were administered subcutaneously daily at the levels noted in the figures and tables. Control animals received the solvent that was used for each of the drugs. After 7-15 days of drug injections or 7-15 days after operation the animals were anesthetized with pentobarbitol sodium and the heart, gastrocnemius, soleus, and diaphragm muscles were quickly excised and placed in icecold 0.9% saline. The hearts were either perfused as working heart preparations (5), homogenized

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Variations in the small subunits of different myosins

Cited by 38 publications

References 3 publications

Activation of the Adenosine Triphosphatase of Limulus polyphemus Actomyosin by Tropomyosin

Activation of the Adenosine Triphosphatase of Limulus polyphemus Actomyosin by Tropomyosin

Light Chains of Myosins from White, Red, and Cardiac Muscles

Hormonal Control of Cardiac Myosin Adenosine Triphosphatase in the Rat

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