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Contribution of the myosin binding protein C motif to functional effects in permeabilized rat trabeculae.

Razumova MV, Bezold KL, Tu AY, Regnier M, Harris SP - J. Gen. Physiol. (2008)

Bottom Line: Myosin binding protein C (MyBP-C) is a thick-filament protein that limits cross-bridge cycling rates and reduces myocyte power output.Recombinant proteins that lacked the combination of C1 and the motif did not affect contractile properties.These results suggest that the C1 domain plus the motif constitute a functional unit of MyBP-C that can activate the thin filament.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of Washington, Seattle, WA 98195, USA.

ABSTRACT
Myosin binding protein C (MyBP-C) is a thick-filament protein that limits cross-bridge cycling rates and reduces myocyte power output. To investigate mechanisms by which MyBP-C affects contraction, we assessed effects of recombinant N-terminal domains of cardiac MyBP-C (cMyBP-C) on contractile properties of permeabilized rat cardiac trabeculae. Here, we show that N-terminal fragments of cMyBP-C that contained the first three immunoglobulin domains of cMyBP-C (i.e., C0, C1, and C2) plus the unique linker sequence termed the MyBP-C "motif" or "m-domain" increased Ca(2+) sensitivity of tension and increased rates of tension redevelopment (i.e., k(tr)) at submaximal levels of Ca(2+). At concentrations > or =20 microM, recombinant proteins also activated force in the absence of Ca(2+) and inhibited maximum Ca(2+)-activated force. Recombinant proteins that lacked the combination of C1 and the motif did not affect contractile properties. These results suggest that the C1 domain plus the motif constitute a functional unit of MyBP-C that can activate the thin filament.

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Related in: MedlinePlus

Effects of C0C2, C1C2, C0C1m, and C1m on total Ca2+-independent and -dependent force. Effects of 10, 20, and 30 μM protein are shown on total force at pCa 4.5 (black bars) and Ca2+-independent force at pCa 9.0 (gray bars). Ca2+-activated force (white bars) is force at pCa 4.5 minus force at pCa 9.0. Washout (Wash) shows force values after a 20-min incubation in relaxing solutions without added proteins.
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fig8: Effects of C0C2, C1C2, C0C1m, and C1m on total Ca2+-independent and -dependent force. Effects of 10, 20, and 30 μM protein are shown on total force at pCa 4.5 (black bars) and Ca2+-independent force at pCa 9.0 (gray bars). Ca2+-activated force (white bars) is force at pCa 4.5 minus force at pCa 9.0. Washout (Wash) shows force values after a 20-min incubation in relaxing solutions without added proteins.

Mentions: Fig. 8 shows effects of increases in [C0C2] on Ca2+-independent force developed in relaxing (pCa 9.0) solutions, total force measured in pCa 4.5 solutions, and maximum Ca2+-activated force (i.e., active force developed in a pCa 4.5 solution minus force measured at pCa 9.0). The data show a trend for concentrations of C0C2 ≥ 10 μM to increase force independent of Ca2+ with activating effects in pCa 9.0 significant at 20 μM C0C2. Total force (Ca2+ dependent and independent) measured at pCa 4.5 was reduced at 30 μM C0C2, and there was a significant decrease in the Ca2+-activated component of force generated at saturating Ca2+ (pCa 4.5). Similar effects were observed for C1C2, C0C1m, and C1m (Fig. 8). All activating and inhibitory effects were reversible after a 20-min washout of proteins from pCa 9.0 and pre-activating solutions. Table II shows summary data for effects of recombinant proteins on force at pCa 9.0 and at pCa 4.5.


Contribution of the myosin binding protein C motif to functional effects in permeabilized rat trabeculae.

Razumova MV, Bezold KL, Tu AY, Regnier M, Harris SP - J. Gen. Physiol. (2008)

Effects of C0C2, C1C2, C0C1m, and C1m on total Ca2+-independent and -dependent force. Effects of 10, 20, and 30 μM protein are shown on total force at pCa 4.5 (black bars) and Ca2+-independent force at pCa 9.0 (gray bars). Ca2+-activated force (white bars) is force at pCa 4.5 minus force at pCa 9.0. Washout (Wash) shows force values after a 20-min incubation in relaxing solutions without added proteins.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2571974&req=5

fig8: Effects of C0C2, C1C2, C0C1m, and C1m on total Ca2+-independent and -dependent force. Effects of 10, 20, and 30 μM protein are shown on total force at pCa 4.5 (black bars) and Ca2+-independent force at pCa 9.0 (gray bars). Ca2+-activated force (white bars) is force at pCa 4.5 minus force at pCa 9.0. Washout (Wash) shows force values after a 20-min incubation in relaxing solutions without added proteins.
Mentions: Fig. 8 shows effects of increases in [C0C2] on Ca2+-independent force developed in relaxing (pCa 9.0) solutions, total force measured in pCa 4.5 solutions, and maximum Ca2+-activated force (i.e., active force developed in a pCa 4.5 solution minus force measured at pCa 9.0). The data show a trend for concentrations of C0C2 ≥ 10 μM to increase force independent of Ca2+ with activating effects in pCa 9.0 significant at 20 μM C0C2. Total force (Ca2+ dependent and independent) measured at pCa 4.5 was reduced at 30 μM C0C2, and there was a significant decrease in the Ca2+-activated component of force generated at saturating Ca2+ (pCa 4.5). Similar effects were observed for C1C2, C0C1m, and C1m (Fig. 8). All activating and inhibitory effects were reversible after a 20-min washout of proteins from pCa 9.0 and pre-activating solutions. Table II shows summary data for effects of recombinant proteins on force at pCa 9.0 and at pCa 4.5.

Bottom Line: Myosin binding protein C (MyBP-C) is a thick-filament protein that limits cross-bridge cycling rates and reduces myocyte power output.Recombinant proteins that lacked the combination of C1 and the motif did not affect contractile properties.These results suggest that the C1 domain plus the motif constitute a functional unit of MyBP-C that can activate the thin filament.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of Washington, Seattle, WA 98195, USA.

ABSTRACT
Myosin binding protein C (MyBP-C) is a thick-filament protein that limits cross-bridge cycling rates and reduces myocyte power output. To investigate mechanisms by which MyBP-C affects contraction, we assessed effects of recombinant N-terminal domains of cardiac MyBP-C (cMyBP-C) on contractile properties of permeabilized rat cardiac trabeculae. Here, we show that N-terminal fragments of cMyBP-C that contained the first three immunoglobulin domains of cMyBP-C (i.e., C0, C1, and C2) plus the unique linker sequence termed the MyBP-C "motif" or "m-domain" increased Ca(2+) sensitivity of tension and increased rates of tension redevelopment (i.e., k(tr)) at submaximal levels of Ca(2+). At concentrations > or =20 microM, recombinant proteins also activated force in the absence of Ca(2+) and inhibited maximum Ca(2+)-activated force. Recombinant proteins that lacked the combination of C1 and the motif did not affect contractile properties. These results suggest that the C1 domain plus the motif constitute a functional unit of MyBP-C that can activate the thin filament.

Show MeSH
Related in: MedlinePlus