BIPN 100 Lecture Notes - Lecture 13: Myosin Head, Thin (Film), Myosin
28 Mar 2018
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Document Summary
Attachment sites for thin filaments, from german zwischen meaning between. 2 chains of f-actin twist around a center core (the nebulin), with tropomyosin wrapping around f-actin. Tropomyosin blocks myosin attachment: giant accessory proteins: titin and nebulin, titin provides elasticity and stabilizes myosin, nebulin helps align actin, relaxed state, myosin head cocked, tropomyosin partially blocks binding site on actin, myosin is weakly bound to actin. Myosin hydrolyzes atp > myosin cocked, binds weakly to actin. Ca2+ increases in cytosol and binds to troponin (tn) Troponin-ca2+ complex pulls tropomyosin away from actin"myosin binding site. Myosin releases pi> head swivels, actin filament moves toward m line: relaxed state: myosin is cocked, ready to fire (weak binding, with calcium binding to troponin and removing tropomyosin, immediate power stroke. Release phosphate (strong binding: adp released, myosin and actin still strongly bound, atp needed to release binding, myosin now free to bind to next g actin. Increase firing of motor neuron to increase tension.
