Sarcoplasmic reticulum calcium pump in cardiac and slow twitch skeletal muscle but not fast twitch skeletal muscle undergoes phosphorylation by endogenous and exogenous Ca2+/calmodulin-dependent protein kinase. Characterization of optimal conditions for calcium pump phosphorylation.

The superior rectus muscles of marlin, swordfish, sailfish, and spearfish are modified for generating heat rather than force. This study focuses on the sarcoplasmic reticulum calcium-adenosinetriphosphatase (SR Ca(2+)-ATPase) to gain further insight into the muscle fiber type origin of the billfish “heater cell.” Direct sequencing and immunolocalization demonstrated that marlin and swordfish epaxial swimming muscles express two forms of the SR Ca(2+)-ATPase in a fiber type-specific manner; red slow-twitch skeletal and cardiac muscles express the same SERCA2 message, whereas white fast-twitch skeletal muscles express a SERCA1 message. Thus the expression pattern of the SR Ca2+ pump is similar in both billfish and tetrapod muscles. Molecular and immunological studies revealed that billfish heater tissue and superior rectus muscle express both fast and slow SR Ca2+ pump isoforms. Immunohistochemical results suggest that heater cells and most extraocular muscle fibers express the fast SR Ca2+ pump. Expression of the fast SR Ca(2+)-ATPase by heater cells has implications for heater cell origin and thermogenic control.

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Preparation and characterization of bovine aortic actin

Biochemical Journal ◽

10.1042/bj2280433 ◽

1985 ◽

Vol 228 (2) ◽

pp. 433-441 ◽

Cited By ~ 13

Author(s):

J C Cavadore ◽

C Axelrud-Cavadore ◽

P Berta ◽

M C Harricane ◽

J Haiech

Keyword(s):

Skeletal Muscle ◽

Smooth Muscle Actin ◽

Original Method ◽

Muscle Actin ◽

Dependent Protein Kinase ◽

Skeletal Muscle Myosin ◽

Tryptophan Residues ◽

Dependent Protein ◽

Muscle Myosin

A functional vascular smooth-muscle actin from bovine aorta was purified to homogeneity by an original method and was able to polymerize. Aortic actin is composed of two major isoforms and at least two minor ones. This actin was not phosphorylated by either cyclic AMP-dependent protein kinase or C kinase. The physical properties of aortic actin were found to be very similar to those of skeletal-muscle actin, except for amino acid composition (three tryptophan residues instead of four). The aortic actin and skeletal-muscle actin differ in the extent of activation of the Mg-dependent ATPase of skeletal-muscle myosin.

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Diazepam reveals different rate-limiting processes in rat skeletal muscle contraction

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y87-048 ◽

1987 ◽

Vol 65 (2) ◽

pp. 272-273 ◽

Cited By ~ 7

Author(s):

Michael Chua ◽

Angela F. Dulhunty

Keyword(s):

Skeletal Muscle ◽

Sarcoplasmic Reticulum ◽

Calcium Binding ◽

Extensor Digitorum Longus ◽

Calcium Uptake ◽

Rat Skeletal Muscle ◽

Skeletal Muscle Contraction ◽

Slow Twitch ◽

Fast Twitch ◽

Rate Limiting

The action of the tranquilizer diazepam on rat skeletal muscle showed that relaxation of isometric twitches is controlled by different processes in extensor digitorum longus (fast-twitch) and soleus (slow-twitch) muscles. Diazepam caused an increase in the amplitude of twitches in fibres from both muscles but increased the twitch duration only in soleus. The amplitude of fused tetani were reduced in both muscles and the rate of relaxation after the tetanus slowed by as much as 34% when the amplitude of the tetanus was reduced by only 11%. The slower tetanic relaxation indicated that calcium uptake by the sarcoplasmic reticulum was slower than normal in slow- and fast-twitch fibres. We conclude therefore that calcium uptake by the sarcoplasmic reticulum is rate limiting for twitch relaxation in slow-twitch but not fast-twitch fibres and suggest that calcium binding to parvalbumin controls relaxation in the fast fibres.

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