KINESIOL 1Y03 Lecture Notes - Lecture 30: Microfilament, Myofilament, Skeletal Muscle
20 Apr 2016
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1st component of actin myofilament: f actin molecules (fibrous actin, long strand of actin): 2 wound together for form helix. Each strand made of globular actins (g actin molecules) Yellow area is the active site: where myosin heads bind and form the cross-bridge. Two regulatory proteins associated with the actin: tropomyosin: regulate availability of active sites for myosin. Coils around actin and covers over the active sites so myosin can"t bind. Tropomyosin is first signalled away so trop can bind: troponin: associatiated with globular and f actin and tropomyosin. 3 subunits at rest: binds to g actin, binds to tropomyosin which is held over active sites, binds calcium important regulatory function. Muscle contraction > release of calcium, pulls tropomyosin off the binding sites. Two heavy chains of protein coiled to form two alpha helices. Rods aligned so they point towards centre of sarcomere > m-line holds the rod portion of the myosin molecules.
