Myosin-containing filaments

Huxley, H. E. (1972). Structural changes in the actin- and myosin-containing filaments during contraction. Cold Spring Harbor Symp. Quant. Biol. 37, 361-376. 

Squire, J. M. (1971). General model for the structure of all myosin-containing filaments. Nature 233, 457 62. 

The A-bands contain both the myosin-containing thick filaments and the actin-containing thin filaments. In the A-bands, each thick filament is surrounded by six thin filaments (Figure 3) such that the two types of filament overlap, although the... 

When myofibrils are examined by electron microscopy, it appears that each one is constructed of two types of longimdinal filaments. One type, the thick filament, confined to the A band, contains chiefly the protein myosin. These filaments are about 16 run in diameter and arranged in cross-section as a hexagonal array (Figure 49-2, center right-hand cross-section). 

Assembly of the actin network merely by interaction with these binding proteins can itself account for pseudopodia formation and propulsive movement. However, there is some evidence to suggest that F-actin-myosin interactions are required for vectorial movement hence it has been demonstrated that pseudopodia contain filament networks comprising actin and myosin. Myosin plays a role in the contractile movement of neutrophils in a... 

In the myosin-containing part of the sarcomere, the A-band, the myosin filaments are cross-linked at the M-band by various additional proteins (Fig. 3F, I)). Details of these are given later in Section II.C. Along the myosin filaments there is also part of the titin molecule (Fig. 5B, D). Titin is the largest known protein with a molecular weight of 3 MDa. It is anchored with its C-terminus at the M-band and its N-terminus at the Z-band. Titin... 

The answer is b. (Murray, pp 48-62. Scriver, pp 3-45. Sack, pp 1-3. Wilson, pp 101-120.) Two kinds of interacting protein filaments are found in skeletal muscle. Thick filaments 15 nm in diameter contain primarily myosin. Thin filaments 7 nm in diameter are composed of actin, troponin, and tropomyosin. The thick and thin filaments slide past one another during muscle contraction. Myosin is an ATPase that binds to thin filaments during contraction, ot-actinin can be found in the Z line. 

Nonmuscle cells contain prominent contractile bundles composed of actin and myosin II filaments. The contractile bundles of nonmuscle cells, which may be transitory or permanent differ in several ways from the noncontractile bundles of actin described earlier in this chapter (see Figure 19-5). Interspersed among the actin filaments of a contractile bundle Is myosin II, which is responsible for their contractility. When Isolated from cells, these bundles contract on the addition of ATP. Contractile bundles are always located adjacent to the plasma membrane as a sheet or belt, whereas noncontractile actin bundles form the core of membrane projections (e.g., microvilli and fllopodla). 

Smooth muscle myosin containing a skeletal myosin RLC, which has a Glu residue at the position corresponding to Arg 16 in the smooth muscle RLC sequence, formed filaments. The small amount of soluble material in equilibrium was only partially folded (Trybus and Lowey, 1988). A chimeric RLC with the N-terminal half of smooth RLC and the C-terminal half of skeletal RLC, despite having a completely native N-terminal half, also formed filaments (Trybus and Chatman, 1993). This result implies that the key N-terminal residues must be properly positioned for the rod to bind. 

Figure 14.10 A muscle viewed under the microscope is seen to contain many myofibrils that show a cross-striated appearance of alternating light and darkbands, arranged in repeating units called sarcomeres. The dark bands comprise myosin filaments and are interupted by M (middle) lines, which link adjacent myosin filaments to each other.

The cytoskeleton also contains different accessory proteins, which, in accordance with their affinities and functions, are designated as microtubule-associated proteins (MAPs), actin-binding proteins (ABPs), intermediate-filament-associated proteins (IFAPs), and myosin-binding proteins. This chapter is focused on those parts of the cytoskeleton that are composed of microfilaments and microtubules and their associated proteins. The subject of intermediate filaments is dealt with in detail in Volume 2. 

Skeletal muscle myosin-Il was first purified in the 1930s and has been extensively studied since (Engelhardt and Ljubimova, 1939). Myosin-II is a dimer composed of two molecules of myosin joined by intertwined, filamentous tails, with each monomer containing two pairs of light chains (Figure 2) (Adelstein and... 

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