Calcium muscle

Moews, P.C., Kretsinger, R.H. Refinement of the structure of carp muscle calcium-binding parvalbumin by model building and difference Fourier analysis. 

In skeletal muscle, calcium binds to troponin and causes the repositioning of tropomyosin. As a result, the myosin-binding sites on the actin become uncovered and crossbridge cycling takes place. Although an increase in cytosolic calcium is also needed in smooth muscle, its role in the mechanism of contraction is very different. Three major steps are involved in smooth muscle contraction ... 

Dick GM, Hunter AC, Sanders KM (2002) Ethylbromide tamoxifen, a membrane-impermeant antiestrogen, activates smooth muscle calcium-activated large-conductance potassium channels from the extracellular side. Mol Pharmacol 61 (5) 1105—1113... 

R. H. Kretsinger and C. F. Nockolds, Carp muscle calcium-binding protein, J. Biol. Chem. 248, 3313-3326 (1973). 

Fig. 56. The calcium-binding sites from carp muscle calcium-binding protein (a) backbone of the entire E-F hand (b) detailed view of the E-F calcium-binding site, including those side chains which are Ca ligands (c) detailed view of the C-D calcium-binding site, rotated to match part b. Oxygens are shown as open circles and a-carbons as solid dots.

Cytochrome c peroxidase domain 1 C. Miscellaneous antiparallel a Carp muscle calcium-binding protein Egg lysozyme Citrate synthase Catalase domain 2 Cytochrome c peroxidase domain 2 p-Hydroxybenzoate hydroxylase domain 3 II. Parallel a/j3 domains... 

Kretsinger, R. H. (1972). Gene triplication deduced from the tertiary structure of a muscle calcium binding protein. Nature (London) New Biol. 240,85-88. 

Calcium play vital role in excitation - contraction coupling in myocardium. Calcium mediates contraction in vascular and other smooth muscles. Calcium is required for exocytosis and also involved in neurotransmitters release. Calcium also help in maintaining integrity of mucosal membranes and mediating cell adhesions. Hypercalcemia may occur in hyperthyroidism, vitamin D intoxication and renal insufficiency, which can be treated by administration of calcitonin, edetate sodium, oral phosphate etc. Hypocalcemia may occur in hypothyroidism, malabsorption, osteomalacia secondary to leak of vitamin D or vitamin D resistance, pancreatitis and renal failure. Hypocalcemia can be treated by chloride, gluconate, gluceptate, lactate and carbonate salts of calcium. 

Important differences between the available calcium channel blockers arise from the details of their interactions with cardiac ion channels and, as noted above, differences in their relative smooth muscle versus cardiac effects. Sodium channel block is modest with verapamil, and still less marked with diltiazem. It is negligible with nifedipine and other dihydropyridines. Verapamil and diltiazem interact kinetically with the calcium channel receptor in a different manner than the dihydropyridines they block tachycardias in calcium-dependent cells, eg, the atrioventricular node, more selectively than do the dihydropyridines. (See Chapter 14 for additional details.) On the other hand, the dihydropyridines appear to block smooth muscle calcium channels at concentrations below those required for significant cardiac effects they are therefore less depressant on the heart than verapamil or diltiazem. 

Protein sequence and structure of troponin (TN-C) and carp muscle calcium binding parvalbumin (MCBP) are known199-201). MCBP has two calcium binding regions each consisting of an a-helix, a loop about the calcium ion and another a-helix, as so-called EF hand (Fig. 21)202,203). 

Compounds with vitamin K activity (Table 6.2) are required in our diets for y-carboxyglutamate biosynthesis (Table 4.1). This amino acid is produced from certain protein glutamyl residues by carboxylation. Proteins that contain y-carboxyglutamate are blood prothrombin and coagulation factors VII, IX, and X (see Chapter 7). Other proteins of this type are osteocalcin from bone and several kidney and muscle calcium-binding proteins. 

Conger JD, Falk SA, Robinette JB Angiotensin ll-induced changes in smooth muscle calcium in rat renal arterioles. J.Am.Soc. Nephrol. 3 1792-1803,1993... 

The answer is b. (A furray, pp 48-73. Scriver, pp 4571-4636. Sack, pp 3—17. Wilson, pp 101-120.) Calcium ions are the regulators of contraction of skeletal muscle. Calcium is actively sequestered in sarcoplasmic... 

Cardiac Muscle. Calcium inhibitory agents may interfere with excitation-contraction coupling processes in myocardial or vascular smooth muscle cells by a number of mechanisms including l) inhibition of the slow inward current through direct competition for slow channels or interference with the membrane binding of Ca2+ 2) interference with the release... 

As a result of their ability to relax smooth muscle, calcium channel blocking drugs have numerous therapeutic applications, mainly in the treatment of cardiovascular disorders but possibly also in therapy for bronchial asthma, gastrointestinal muscle spasms and uterine disorders. The in vivo effects of the... 

The isolated renal vessel technique has been modified so that vessels can be isolated from rats instead of rabbits [256]. The preparation has also been modified for fluorescence measurements of cytosolic calcium in the smooth muscle cell layer [257]. Measurements of changes in smooth muscle calcium can be carried out simultaneously with determinations of changes in lumen diameters. The effects of various agonists and pressure stimulation in the presence and absence of pharmacologic agents can be determined. Angiotensin... 

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