BIOL 4510 Lecture : lec 13
Document Summary
Four contractile proteins are phosphorylated: tn-i, c-protein, tn-t, and mlc-2. Phosphorylation by pka occurs in n-terminal region of tn-i; unique to cardiac tn-i. Tn-i phosphorylation: phosphorylated by pka reduces affinity of ca2+ binding to. Tn-c by enhancing ca2+ unbinding rates causes rightward shift in force-[ca2+] relationship. By phosphorylating tn-i, the rates of ca2+ binding and unbinding from contractile proteins is enhanced, thereby increasing rates of pressure and force relaxation. Figure 25: effects of beta-adrenergic stimulation (activation of pka) on the force-ca2+ relationship. Pka-dependent phosphorylation of mybpc and mlc-2 are also critical for ensuring proper responses of the contractile system to increased demand for cardiac output. Ca2+ cooperativity in contraction of cardiac muscle steady-state force-[ca2+] relationship are characterized/quantified by the hill equation: When a parameter (like force) depends strongly on the concentration of the a substance, biochemists characterize these properties as reflecting (cid:179)(cid:70)(cid:82)(cid:82)(cid:83)(cid:72)(cid:85)(cid:68)(cid:87)(cid:76)(cid:89)(cid:76)(cid:87)(cid:92)(cid:180). A famous example of cooperativity is o2 binding to hemoglobin.
