Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Skeletal muscle contractile proteins

Seene T. Turnover of skeletal muscle contractile proteins in glucocorticoid myopathy. J Steroid Biochem Mol Biol. 1994 50 IM. [Pg.432]

The principal molecular constituent of thin filaments is actin. Actin has been highly conserved during the course of evolution and is present in all eukaryotes, including single-celled organisms such as yeasts. Actin was first extracted and purified from skeletal muscle, where it forms the thin filaments of sarcomeres. It also is the main contractile protein of smooth muscle. Refined techniques for the detection of small amounts of actin (e.g., immunofluorescence microscopy, gel electrophoresis, and EM cytochemistry) subsequently confirmed the presence of actin in a great variety of nonmuscle cells. Muscle and nonmuscle actins are encoded by different genes and are isoforms. [Pg.21]

Contractile proteins which form the myofibrils are of two types myosin ( thick filaments each approximately 12 nm in diameter and 1.5 (im long) and actin ( thin filaments 6nm diameter and 1 (Am in length). These two proteins are found not only in muscle cells but widely throughout tissues being part of the cytoskeleton of all cell types. Filamentous actin (F-actin) is a polymer composed of two entwined chains each composed of globular actin (G-actin) monomers. Skeletal muscle F-actin has associated with it two accessory proteins, tropomyosin and troponin complex which are not found in smooth muscle, and which act to regulate the contraction cycle (Figure 7.1). [Pg.233]

Smooth muscle effects. The opposing effects on smooth muscle (A) of a-and p-adrenoceptor activation are due to differences in signal transduction (p. 66). This is exemplified by vascular smooth muscle (A). ai-Receptor stimulation leads to intracellular release of Ca + via activation of the inositol tris-phosphate (IP3) pathway. In concert with the protein calmodulin, Ca + can activate myosin kinase, leading to a rise in tonus via phosphorylation of the contractile protein myosin. cAMP inhibits activation of myosin kinase. Via the former effector pathway, stimulation of a-receptors results in vasoconstriction via the latter, P2-receptors mediate vasodilation, particularly in skeletal muscle - an effect that has little therapeutic use. [Pg.84]

Smooth muscle differs from skeletal muscle in various ways. Smooth muscles—which are found, for example, in blood vessel walls and in the walls of the intestines—do not contain any muscle fibers. In smooth-muscle cells, which are usually spindle-shaped, the contractile proteins are arranged in a less regular pattern than in striated muscle. Contraction in this type of muscle is usually not stimulated by nerve impulses, but occurs in a largely spontaneous way. Ca (in the form of Ca -calmodulin see p.386) also activates contraction in smooth muscle in this case, however, it does not affect troponin, but activates a protein kinase that phosphorylates the light chains in myosin and thereby increases myosin s ATPase activity. Hormones such as epinephrine and angiotensin II (see p. 330) are able to influence vascular tonicity in this way, for example. [Pg.338]

Johnston, I.A. (1983). Comparative studies of contractile proteins from the skeletal and cardiac muscles of lower vertebrates. Comparative Biochemistry and Physiology 76A, 439-445. [Pg.280]

The contractile proteins of the myofibril include three troponin regulatory proteins. The troponin complex includes three protein subunits, troponin C (the calcium-binding component), troponin I (the inhibitory component), and troponin T (the tropomyosin-binding component). The subunits exist in a number of isoforms. The distribution of these isoforms varies between cardiac muscle and slow- and fast-twitch skeletal muscle. Only two major isoforms of troponin C are found in human heart and skeletal muscle. These are characteristic of slow- and fast-twitch skeletal muscle. The heart isoform is identical with the slow-twitch skeletal muscle isoform. Isoforms of cardiac-specific troponin T (cTnT) and cTnl also have been identified and are the products of unique genes. All cardiac troponins are localized primarily in the myofibrils (94%-97%), with a smaller cytoplasm fraction (3%-6%). [Pg.56]

Skeletal muscle moves the bones attached to joints. These muscles are composed of bundles of long, multinucleated cells. The cytoplasm contains a high concentration of a special macromolecular contractile-protein complex, actomyosin (Chap. 5). There is also an elaborate membranous network called the sarcoplasmic reticulum that has a high Ca2+ content. The contractile-protein complex has a banded appearance under microscopy. [Pg.17]

The creatine synthesized in the liver is transported through the bloodstream to skeletal and heart muscle. It enters the mitochondria, where it is phosphorylated to crealine-P Creatine kinase catalyzes this reversible addition of a phosphate group, as shown in Figure 4.34. Creatine-P is unique in that its only known function is as an energy buffer. The creatine P formed in the mitochondria travels to the contractile proteins in the cytoplasm of the muscle fiber. The polymer, or complex, of contractile proteins is called a myofibril. Contraction of a myofibril is coupled to the hydrolysis of ATP to ADP. The immediate replenishment of ATP is catalyzed by a second creatine kinase, residing on the myofibril, that catalyzes the conversion of creatine-P to creatine. This reversal of the reaction takes place in the... [Pg.201]

Anabolic steroids decrease catabolism and increase skeletal muscle protein synthesis. Whether this results in muscular hypertrophy or hyperplasia, or a combination of these, is unclear and probably depends upon the muscle studied. Different muscle types contain different cytosolic receptor numbers and, therefore, the response to anabolic steroids varies. Anabolic steroids initiate an increase in RNA polymerase activity and the synthesis of either structural or contractile proteins. In some muscles, anabolic steroids may increase the ratio of fast twitch to slow twitch fibers (Nimmo et al 1982, Snow et al 1982). Increased activity of enzymes involved in energy metabolism may also occur. However, the total glycogen content may remain unchanged (Hyyppa et al 1997). The effects are most profound in females and castrated males (Snow 1993). [Pg.143]

The striations in skeletal muscle are attributable to the presence and organization of myofibrils in the cells. Myofibrils are thread-like structures consisting of thin and thick filaments. The contractile proteins actin and myosin are contained within the filaments myosin within the thick filaments, actin within the thin filaments. The sliding of these filaments relative to each other, using myosin-catalyzed ATP hydrolysis as an energy source, allows for the contraction and relaxation of the muscle (see Fig. 19.4). [Pg.863]

Swynghedauw B (1986) Developmental and functional adaptation of contractile proteins in cardiac and skeletal muscle. Physiol Rev 66 710-770... [Pg.295]

Fresh or Frozen Tissue and Cells Human cell cultures and most human tissues can be efficiently lysed using lysis buffer and protease or proteinase K. Fresh or frozen tissue samples should be cut into small pieces to aid the lysis. Mechanical disruption using a homogenizer, mixer mill, or mortar and pestle prior to lysis can also reduce the lysis time. Skeletal muscle, heart, and skin tissue have an abundance of contractile proteins, connective tissue, and collagen, and special care should be taken to ensure complete digestion using protease or proteinase K. [Pg.92]

Actin and myosin are the principal contractile proteins of the three different t es of vertebrate muscle skeletal (or striated) muscle, cardiac muscle and smooth (non-striated) muscle. Muscle protein makes up approximately 40% of body protein. Actin comprises about 25% and myosin about 50% of myofibrillar protein. In striated muscles, myosin is the principal protein of the thick filaments, and actin the thin filaments. Shortening of the myofibrils is achieved by sliding the thick and thin filaments to increase the overlap between them (see Rayment Holdea 1994). Many of the other proteins assist in this process (see Harold, 1986). Actin and myosin also occur in non-muscle cells, but their spatial organisation is more variable and less regular and... [Pg.151]

Zyma VL, Miroshnichenko NS, Danilova VM et al (1988) Interactirai of ilavraioid compounds with contractile proteins of skeletal muscle. Gen Physiol Biophys 7 165—175... [Pg.1843]

Nitric oxide- or peroxynitrite-mediated neuronal injury involves damages to DNA with the subsequent activation of the nuclear protein, poly(ADP-ribose)synthetase (PARS) (Zhang et al. 1994). Evidence is also growing that nNOS is also present in skeletal muscle where it is involved in the regulation of metabolism and muscle contractility. [Pg.65]


See other pages where Skeletal muscle contractile proteins is mentioned: [Pg.292]    [Pg.160]    [Pg.147]    [Pg.109]    [Pg.282]    [Pg.301]    [Pg.10]    [Pg.182]    [Pg.141]    [Pg.209]    [Pg.164]    [Pg.516]    [Pg.208]    [Pg.208]    [Pg.339]    [Pg.458]    [Pg.488]    [Pg.182]    [Pg.133]    [Pg.346]    [Pg.64]    [Pg.513]    [Pg.703]    [Pg.705]    [Pg.32]    [Pg.469]    [Pg.585]    [Pg.63]    [Pg.138]    [Pg.549]   
See also in sourсe #XX -- [ Pg.292 ]




SEARCH



Contractile

Contractile protein

Contractility

Muscle contractile

Muscle proteins

Skeletal muscle

Skeletal muscle protein

© 2024 chempedia.info