हिंदी
Tamil Nadu Board of Secondary EducationHSC Science Class 11

Structure of Contractile Proteins

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Estimated time: 3 minutes
CBSE: Class 12

Key Points: Structure of Contractile Proteins

  • Each thin filament (actin) is made of two 'F' (Filamentous) actins helically wound together. Each 'F' actin is a polymer of monomeric 'G' (Globular) actins.
  • Two tropomyosin filaments run alongside 'F' actins. Troponin proteins are distributed at regular intervals on tropomyosin.
  • In the resting state, a troponin subunit masks the active binding sites for myosin on actin filaments.
  • Each thick filament (myosin) is made of many monomeric proteins called meromyosins. Each meromyosin has a globular head, short arm, and tail.
  • Meromyosin is of two types - HMM (Heavy Meromyosin) - the globular head + short arm, and LMM (Light Meromyosin) - the tail.
  • The globular head (HMM) projects outward, forming a cross arm. It acts as an active ATPase enzyme and has binding sites for both ATP and actin.
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