Cross bridge

Myosin heads form cross-bridges between the actin and myosin filaments... 

Within each sarcomere the relative sliding of thick and thin filaments is brought about by "cross-bridges," parts of the myosin molecules that stick out from the myosin filaments and interact cyclically with the thin actin filaments, transporting them hy a kind of rowing action. During this process, the hydrolysis of ATP to ADP and phosphate couples the conformational... 

Figure 14.12 The swinging cross-bridge model of muscle contraction driven by ATP hydrolysis, (a) A myosin cross-bridge (green) binds tightly in a 45 conformation to actin (red), (b) The myosin cross-bridge is released from the actin and undergoes a conformational change to a 90 conformation (c), which then rebinds to actin (d). The myosin cross-bridge then reverts back to its 45° conformation (a), causing the actin and myosin filaments to slide past each other. This whole cycle is then repeated.

Time-resolved x-ray diffraction of frog muscle confirmed movement of the cross-bridges... 

The structure of myosin supports the swinging cross-bridge hypothesis... 

Figure 14.17 A sequence of events combining the swinging cross-bridge model of actin and myosin filament sliding with structural data of myosin with and without bound nucleotides.

Intrachain S—S (disulfide) cross-bridges between cysteine residues in the polypeptide chain are cleaved. (If these disulfides are interchain linkages, then step 2 precedes step 1.)... 

The positions of S—S cross-bridges formed between cysteine residues are located. 

FIGURE 5.17 The hormone insulin consists of two polypeptide chains, A and B, held together by two disulfide cross-bridges (S—S). The A chain has 21 amino acid residues and an intrachain disulfide the B polypeptide contains 30 amino acids. The sequence shown is for bovine insulin. 

Warner, F.D. Mitchell, D.R. (1981). Polarity of dynein-microtubule interactions in vitro Cross-bridging between parallel and antiparallel microtubules. J. Cell Biol. 89, 35-44. 

Wang, E. (1985). Are cross-bridging strucmres involved in the bundle formation of intermediate filaments and the decrease in locomotion that accompany cell aging J. Cell Biol. 100,1466-1473. 

Dantzig, J.A., Goldman, Y.E., Millar, N.C., Lacktis, J., Homsher, E. (1992). Reversal of the cross-bridge force-generating transition by photogeneration of phosphate in rabbit psoas muscle fibers. J. Physiol. 451,247-278. 

Reedy, M.K., Holmes, K.C., T regear, R.T. (1965). Induced changes in orientation of the cross-bridges of glycerinated insect flight muscle. Nature 207, 1276-1278. 

The Sliding Filament Cross-Bridge Model Is the Foundation on Which Current Thinking About Muscle Contraction Is Built... 

How can hydrolysis of ATP produce macroscopic movement Muscle contraction essentially consists of the cychc attachment and detachment of the S-1 head of myosin to the F-actin filaments. This process can also be referred to as the making and breaking of cross-bridges. The attachment of actin to myosin is followed by conformational changes which are of particular importance in the S-1 head and are dependent upon which nucleotide is present (ADP or ATP). These changes result... 

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