Effect of ageing of myosin on its ability to form synthetic filaments and on proteolysis of the LC2 light chain

Pinset-Härström, I.; Whalen, Robert G.

doi:10.1016/0022-2836(79)90420-0

Cited by 20 publications

(8 citation statements)

References 16 publications

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“…Our results show no such influence on the stability of the filaments formed by skeletal myosin, at least with respect to salt concentration, but the dependence of turbidity on phosphorylation (Figure 6) must be taken to reflect a structural disturbance. That the light chain affects thick-filament structure is evident from the work of Pinset-Harstrom & Whalen (1979), and we find, in agreement with their observations, that reproducibility of the results is critically dependent on integrity of the light chains and thus on the use of fresh myosin preparations, especially in the dephosphorylated form. Pinset-Harstrom & Truffy (1979) have furthermore found that calcium and magnesium have a regulatory effect on thick-filament structure and that the size of synthetic filaments depends on the identity of the divalent cations present.…”

Section: Discussionsupporting

confidence: 89%

“…As matters now stand then, the functional role of calcium binding, of phosphorylation, and indeed of the regulatory light chain in general in vertebrate striated muscle is a matter of conjecture. The light chain evidently exerts an effect on intrafilament interactions between myosin molecules (Pinset-Hartstrom & Whalen, 1979). There is also a certain amount of evidence that it in some manner moderates the interaction of the myosin heads with actin (Margossian et al, 1975;Pemrick, 1977;Malhotra et al, 1979;Craig et al, 1980).…”

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confidence: 99%

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Conformational effects of cation binding to myosin and their relation to phosphorylation

Kardami¹,

Gratzer²

1982

Biochemistry

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Binding profiles of calcium or magnesium ions to rabbit skeletal myosin can be determined from the change in the products of chymotryptic digestion with concentration of the ion. Qualitatively similar effects are brought about by sodium ions at much higher concentrations, and the profiles follow expectations for stoichiometric binding of the univalent ion. The affinity for sodium ions depends on the phosphorylation state of the metal-binding ("regulatory") light chain. The degree of saturation at physiological ionic strength is substantially higher for the phosphorylated form than for the unphosphorylated form. This effect can account quantitatively for the apparent difference in affinity for calcium ions between these two states, ,measured at physiological sodium ion concentration. Thus if phosphorylation of the light chain leads to a structural perturbation linked to the binding of cations, this may be presumed to come about by way of a net change in occupancy of the cation binding sites rather than through displacement of a resident ion by calcium. A similar pattern of behavior is displayed by cardiac myosin. Like calcium or magnesium, sodium ions are found to protect the proteolytically labile sites in the metal-binding light chain itself and at the head-rod junction, and they promote scission in the putative hinge region, with liberation of heavy meromyosin. The digestion pattern is, under the conditions employed here, C A T I O N B I N D I N G T O M Y O S I N V O L . 2 1 , N O . 6 , 1 9 8 2

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Section: Discussionsupporting

confidence: 89%

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confidence: 99%

Conformational effects of cation binding to myosin and their relation to phosphorylation

Kardami¹,

Gratzer²

1982

Biochemistry

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“…These results support the hypothesis that CAF degrades the head region of the myosin heavy chain. These results should not be interpreted as part of the hypothesis advanced by some investigators (8,36) that loss of L2 alters the filamentous structure of myosin. Differential proteolysis by CAF of native as compared to L2-deficient myosin was qualitatively unaffected by the state of aggregation of myosin (Fig.…”

Section: And 5 MM Ca 2+ (Not Shown)mentioning

confidence: 59%

Qualitative analysis of skeletal myosin as substrate of Ca2+-activated neutral protease: comparison of filamentous and soluble, native, and L2-deficient myosin.

Pemrick¹,

Grebenau²

1984

The Journal of Cell Biology

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Ca2+-activated neutral protease (CAF) was capable of degrading myosin over a 200-fold range of protease concentrations. CAF selected the heavy chain of myosin, although either prolonged exposure to or high concentrations of the protease degraded the L1, but not the L2 or L3, light chains of myosin. The following results indicated that during the first hour of digestion, under conditions where native myosin was the substrate, CAF selected for the "head" region of the myosin heavy chain: (a)large heavy chain fragments of identical molecular weight were produced from filamentous and from soluble myosin; (b) light meromyosin was not a substrate; (c) agents known to bind to the head of myosin (actin, MgATP, and L2) had both a qualitative and quantitative effect on degradation; and (d) similar cleavage sites could be demonstrated for myosin and for heavy meromyosin (HMM) despite the fact that HMM was a much poorer substrate than myosin. This observation is interpreted as an indication that the conformation of myosin heavy chain is altered in the preparation of HMM. The principal cleavage sites on the heavy chain of myosin were 20,000, 35,000 and 50,000 D from the Nterminus, producing large fragments with molecular weights of 180,000, 165,000, and 150,000 which comprised a "nicked" species of myosin. This nicked species retained both normal solubility properties and normal hydrolytic activities. For this reason, it is concluded that "nicked myosin" is an important pathophysiological species.

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“…However, the amounts of LC3f in these three samples was somewhat high relative to the amounts of LCjf present and may indicate the presence of some LC2 break-down products which co-migrated with the LC3f peak (Pinset-Harstrom & Whalen, 1979). TABLE 1.…”

Section: Resultsmentioning

confidence: 89%

Mechanical properties and myosin light chain composition of skinned muscle fibres from adult and new‐born rabbits.

Julian¹,

Moss²,

Waller³

1981

The Journal of Physiology

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1. The maximum velocity of shortening, Vmax, and stiffness were measured in skinned single fibre segments from psoas and soleus muscles of adult rabbits and psoas muscles of new‐born rabbits, and the myosin light chain composition was also determined in the same segments used in the mechanical studies. 2. Vmax was obtained at 15 degrees C during maximal activation at pCa 5.49 using a method involving measurement of the time required to take up various amounts of slack imposed on the segments. Stiffness was measured during activation at 10 degrees C by application of length steps complete in 0.6 msec. The myosin light chain composition of the segments was then determined by SDS‐polyacrylamide gel electrophoresis. 3. Only fast type light chains were found to be present in the psoas fibre segments, though the relative amounts of myosin LC1f, LC2f and LC3f in these segments was somewhat variable. In most instances, the sum of the amounts of LC1f and LC3f present was equivalent to the amount of LC2f. Only slow type light chains were found in the soleus segments and the sum of the amounts of LC1as and LC1bs was about equal to the amount of LC2s. 4. The results indicate that there are no consistent relationships between Vmax, tension development or stiffness and LC1f/LC2f in the segments from adult and new‐born psoas muscles, or between these mechanical parameters and LC1as/LC2s or LC1bs/LC2s in the adult soleus segments. However, the psoas segments, which had light chains of the fast type, had Vmax values that were consistently higher than those of the soleus segments, which had light chains of the slow type. 5. The stiffness values obtained in each of the three kinds of muscle were similar, suggesting that cross‐bridge stiffness is similar in rabbit skeletal muscles of different type and age. Moreover, the results indicate that the amount of end compliance introduced by the connections to the fibre segments has a marked influence on the stiffness that is measured.

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Effect of ageing of myosin on its ability to form synthetic filaments and on proteolysis of the LC2 light chain

Cited by 20 publications

References 16 publications

Conformational effects of cation binding to myosin and their relation to phosphorylation

Conformational effects of cation binding to myosin and their relation to phosphorylation

Qualitative analysis of skeletal myosin as substrate of Ca2+-activated neutral protease: comparison of filamentous and soluble, native, and L2-deficient myosin.

Mechanical properties and myosin light chain composition of skinned muscle fibres from adult and new‐born rabbits.

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