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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: 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.

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: 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.

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