Muscle regulatory

Puri, P.L. and Sartorelli, V. (2000) Regulation of muscle regulatory factors by DNA-binding, interacting proteins, and post-transcriptional modifications, /ourmil of Cellular Physiology, 185, 155-173. 

Matsudaira, 1991). These domains have been named calponin homology or CH domains (Castresana and Saraste, 1995) based on the sequence similarity to the smooth muscle regulatory protein calponin (Winder and Walsh,... 

The calponin homology (CH) domain has been identified in many molecules of differing function. However, its presence usually signifies an interaction of some sort with the actin cytoskeleton via an association with F-actin. The domain was initially identified as a 100-residue motif found at the N-terminus of the smooth muscle regulatory protein calponin and, hence, was termed the CH domain (Castresana and Saraste, 1995). The refinement of algorithms for the identification of distinct protein motifs has allowed the identification of CH domains in proteins that range... 

Pena, T. L., and Rane, S. G. 1997. The small conductance calcium-activated potassium channel regulates ion channel expression in C3H10T1/2 cell ectopically expressing the muscle regulatory factor MRF4. J. Cell. Biochem. 272 21909-21916. 

Marston SB, Redwood CS (1992) Inhibition of actin-tropomyosin activation of myosin MgATPase activity by the smooth muscle regulatory protein caldesmon. J Biol Chem 267 1679616800... 

Characterizing inhibitors of calmodulin activation of M LCK-catalyzed phosphorylation of the smooth-muscle regulatory chain... 

Totsukawa G, Himi-Nakamura E, Komatsu S, Iwata K, Tezuka A, Sakai H, Yazaki K, Hosoya H. 19%. Mitosis-specific phosphorylation of smooth muscle regulatory light chain of myosin II at Ser-1 and/ or -2 and Thr-9 in sea urchin egg extract. Cell Struct Funct 21(6) 475-482. 

Y. Lu, C. M. Jeffries and J. Trewhella, Invited Review Probing the Structures of Muscle Regulatory Proteins Using SmaU-Angle Solution Scattering , Biopolymers, 2011, 95, 505. 

Herzberg, O., James, M.N.G. Structure of the calcium regulatory muscle protein troponin-C at 2.8 A resolution. Nature 313 653-659, 1985. 

Reseaich in physiology caiiied out in the 1930s established that the lipid fraction of semen contains small fflnounts of substances that exert powerful effects on smooth muscle. Sheep prostate glands proved to be a convenient source of this material and yielded a mixture of structurally related substances refened to collectively as prostaglandins. We now know that prostaglandins are present in almost all animal tissues, where they cany out a variety of regulatory functions. 

Muscle glycogen phosphorylase is a dimer of two identical subunits (842 residues, 97.44 kD). Each subunit contains a pyridoxal phosphate cofactor, covalently linked as a Schiff base to Lys °. Each subunit contains an active site (at the center of the subunit) and an allosteric effector site near the subunit interface (Eigure 15.15). In addition, a regulatory phosphorylation site is located at Ser on each subunit. A glycogen-binding site on each subunit facilitates prior association of glycogen phosphorylase with its substrate and also exerts regulatory control on the enzymatic reaction. 

In addition to the major proteins of striated muscle (myosin, actin, tropomyosin, and the troponins), numerous other proteins play important roles in the maintenance of muscle structure and the regulation of muscle contraction. Myosin and actin together account for 65% of the total muscle protein, and tropomyosin and the troponins each contribute an additional 5% (Table 17.1). The other regulatory and structural proteins thus comprise approximately 25% of the myofibrillar protein. The regulatory proteins can be classified as either myosin-associated proteins or actin-associated proteins. 

Adapted from Ohtsuki, L, Maruyama, K., and Eba.shi, S., 1986. Regulatory and cyto.skeletal protein.s of vertebrate. skeletal muscle. Advances in Protein Chemistry 38 1-67. 

Smooth muscle myosin phosphatase contains tree subunits, a 110-130 kDa myosin phosphatase targeting and regulatory subunit (MYPT1), a 37 kDa catalytic subunit (PP-1C) and a 20 kDa subunit of unknown function. 

Smooth muscle myosin contains two myosin light chains. Phosphorylation of the regulatory light chain by myosin light chain kinase is a mandatory step to induce contraction. 

The RyR channels seem to be regulated by luminal Ca2+. Luminal Ca2+ may activate theRyR2 channels in the heart. The association of calsequestrin with RyR2 via triadin or junctin is proposed as a possible regulatory mechanism. Such activation by luminal Ca2+ remains controversial in the skeletal muscle. 

Calcium-dependent regulation involves the calcium-calmodulin complex that activates smooth muscle MLCK, a monomer of approximately 135 kDa. Dephosphorylation is initiated by MLCP. MLCP is a complex of three proteins a 110-130 kDa myosin phosphatase targeting and regulatory subunit (MYPT1), a 37 kDa catalytic subunit (PP-1C) and a 20 kDa subunit of unknown function. In most cases, calcium-independent regulation of smooth muscle tone is achieved by inhibition of MLCP activity at constant calcium level inducing an increase in phospho-rMLC and contraction (Fig. 1). 

Somatostatin is a regulatory cyclic peptide, which has originally been described as a hypothalamic growth hormone release-inhibiting factor. It is produced throughout the central nervous system (CNS) as well as in secretoty cells of the periphery and mediates its regulatory functions on cellular processes such as neurotransmission, smooth muscle contraction, secretion and cell proliferation via a family of seven transmembrane domain G-protein-coupled receptors termed sstx 5. 

---