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troponin
Function:
- thin filament regulatory complex which confers Ca+2 sensitivity to striated muscle actomyosin ATPase activity
- Ca+2 controls muscle contraction by an allosteric mechanism in which the flow of information is: Ca+2 -> troponin -> tropomyosin -> actin -> myosin
Structure:
- troponin is a trimeric complex of:
- troponin-C
- troponin-I
- troponin-T
Compartment:
- located in thin muscle filaments at intervals of 38.5 nm, a period set by tropomyosin
Interactions
molecular events
General
contractile protein
cytoskeletal protein
multisubunit protein
Properties
SIZE: MW = 76 kD
COMPARTMENT: cytoplasm
SUBUNITS: troponin-C
MOTIF: acetylation site
SITE: N-TERMINUS
EFFECTOR-BOUND: acetyl
Ca+2-binding site (2)
SITE: N-TERMINAL
Ca+2-binding site (2)
SITE: C-TERMINAL
EFFECTOR-BOUND: Ca+2
troponin-I
MOTIF: Ca+2-binding site
phosphorylation site
actin-binding site
FOR-BINDING-OF: F-actin
troponin-T
MOTIF: Ca+2-binding site
binding site
FOR-BINDING-OF: tropomyosin
References
Textbook of Biochemistry with Clinical Correlations,
3rd ed., TM Devlin (ed), Wiley-Liss, NY 1992 pg 961
Components
troponin-C
troponin-I
troponin-T