BIOL 201 Lecture Notes - Lecture 23: Titin, Endoplasmic Reticulum, Cell Membrane
23 Apr 2016
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Document Summary
Myosin binds atp, hydrolyzes and then release of phosphate group is coupled to conformational change. Sarcomeres are tightly packed arrays of actin filaments and myosin filaments. When muscle receives stimulation the sarcomeres undergo contraction quite rapidly. Actin filament + end attaches to z disk, - end extends away. Myosin head movement against actin cables drive z disks closer together. Power stroke is understood at atomic resolution xray diffraction studies. Neck domain of myosin acts as a lever: experiment: genetically engineering a longer neck and attach to glass slide, the longer the neck (lever) the higher velocity. Muscles face 3 design challenges: prevent continuous contraction: needs atp to dissociate, activate contraction: through phosphate released after hydrolysis, freeze the structure of the sarcomere: attaching actin cables to the z disks. Myosin must remain in the middle of the sarcomere, done by long filamentous proteins: capz at + end and end tropomodulin, nebulin protein extends from capz to tropomodulin.
