Actin regulatory proteins

Figure 2. Scheme for the addition and loss of actin-ATP or actin-ADP from the barbed and pointed ends of an actin filament. The barbed end is the faster growing and more stable end of an actin filament. While the exchange of actin-ADP with ATP to yield actin-ATP and ADP is shown here as a spontaneous process, the actin regulatory protein profilin greatly accelerates the exchange process. Note also that hydrolysis is thought to occur after (and not coincident with) addition of actin-ATP at either end. 

A calcium-regulated actin regulatory protein that binds to and severs actin hlaments, thereby controlling the gel-sol transitions of the actin cytoskeleton. After severing... 

ACTIN REGULATORY PROTEINS Lateral diffusibility of molecules within membranes,... 

ACTIN REGULATORY PROTEINS MONOMOLECULARITY Monomolecular surface coverage, BIOMINERALIZATION MONOPHENOL MONOOXYGENASE... 

McGough, A.M., C.J. Staiger, J.K. Min, and K.D. Simonetti. 2003. The gelsolin family of actin regulatory proteins modular structures, versatile functions. FEBS Lett. 552 75-81. 

Tuba, A GEF for CDC42, Links Dynamin to Actin Regulatory Proteins... 

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. 

Regulatory proteins Major Tropomyosin 33 X 2 5 I band Binds to actin and... 

The calcium mediated contraction of smooth muscle, which unlike striated muscle does not contain troponin, is quite different and requires a particular calcium-binding protein called calmodulin. Calmodulin (CM) is a widely distributed regulatory protein able to bind, with high affinity, four Ca2+ per protein molecule. The calcium—calmodulin (CaCM) complex associates with, and activates, regulatory proteins, usually enzymes, in many different cell types in smooth muscle the target regulatory proteins are caldesmon (CDM) and the enzyme myosin light chain kinase (MLCK). As described below, CaCM impacts on both actin and myosin filaments. 

A cytoskeletal regulatory protein that attaches laterally to actin filament without resulting in filament cross-linking and/or bundling. These include troponin, tropomyosin, calponin, tropomodulin, adducin, caldesmon, and hisactophilin. See also ABM-1 ABM-2 Sequences in Actin-Based Motors Actin-Based Bacterial Motility Actin Assembly Kinetics... 

A cytoskeletal regulatory protein that binds to and cleaves actin filaments. These proteins do not catalyze... 

The regulatory proteins troponin and tropomyosin 1118 Table 19-1 Some Actin-Binding Proteins... 

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... 

Maekawa, S., and H. Sakai. 1990. Inhibition of actin regulatory activity of the 74-kDa protein from bovine adrenal medulla (adseverin) by some phospholipids. J Biol Chem. 265 10940-2. 

Yin, H.L., and T.P. Stossel. 1979. Control of cytoplasmic actin gel-sol transformation by gelsolin, a calcium-dependent regulatory protein. Nature. 281 583-6. 

The muscle sarcomere contains the principal contractile proteins myosin and actin (Fig. 3A to C), which on their own can produce force and movement, together with a number of cytoskeletal and regulatory proteins. The latter include titin, C-protein (MyBP-C), tropomyosin, troponin, a-actinin, myomesin, M-protein, and so on. Some of these help to organize the myosin and actin filaments in the sarcomere, some to define the filament lengths and structure, some to regulate activity, and some to modulate the actin-myosin interaction when the muscle is active. 

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