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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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The combination of C1 and the MyBP-C motif is required to increase Ca2+ sensitivity of tension. (A) 10 μM mC2 (triangles; n = 4) had no effect on tension–pCa relationships relative to control (circles), whereas 5 μM C1m (squares; n = 6) significantly increased Ca2+ sensitivity of tension (ΔpCa50 = 0.12 ± 0.04). (B) 10 μM C0C1 (triangles; n = 3) had no effect on tension–pCa relationships relative to control (circles), whereas 5 μM C0C1m (squares; n = 4) significantly increased Ca2+ sensitivity of tension (ΔpCa50 = 0.27 ± 0.05).
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fig4: The combination of C1 and the MyBP-C motif is required to increase Ca2+ sensitivity of tension. (A) 10 μM mC2 (triangles; n = 4) had no effect on tension–pCa relationships relative to control (circles), whereas 5 μM C1m (squares; n = 6) significantly increased Ca2+ sensitivity of tension (ΔpCa50 = 0.12 ± 0.04). (B) 10 μM C0C1 (triangles; n = 3) had no effect on tension–pCa relationships relative to control (circles), whereas 5 μM C0C1m (squares; n = 4) significantly increased Ca2+ sensitivity of tension (ΔpCa50 = 0.27 ± 0.05).

Mentions: We next investigated whether the Ca2+-sensitizing effects of the motif required the presence of the flanking regions C1 or C2. We therefore generated protein constructs that combined the motif with one or the other of the flanking domains, i.e., C1m or mC2. As shown in Fig. 4 A, the C1m construct was effective at inducing a leftward shift of the force–pCa relationship, whereas mC2 at a comparable concentration failed to induce a leftward shift. Collectively, these results suggest that the motif plus C1, but not the motif plus C2, are necessary for the Ca2+-sensitizing effects of C1C2.


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)

The combination of C1 and the MyBP-C motif is required to increase Ca2+ sensitivity of tension. (A) 10 μM mC2 (triangles; n = 4) had no effect on tension–pCa relationships relative to control (circles), whereas 5 μM C1m (squares; n = 6) significantly increased Ca2+ sensitivity of tension (ΔpCa50 = 0.12 ± 0.04). (B) 10 μM C0C1 (triangles; n = 3) had no effect on tension–pCa relationships relative to control (circles), whereas 5 μM C0C1m (squares; n = 4) significantly increased Ca2+ sensitivity of tension (ΔpCa50 = 0.27 ± 0.05).
© Copyright Policy
Related In: Results  -  Collection

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

fig4: The combination of C1 and the MyBP-C motif is required to increase Ca2+ sensitivity of tension. (A) 10 μM mC2 (triangles; n = 4) had no effect on tension–pCa relationships relative to control (circles), whereas 5 μM C1m (squares; n = 6) significantly increased Ca2+ sensitivity of tension (ΔpCa50 = 0.12 ± 0.04). (B) 10 μM C0C1 (triangles; n = 3) had no effect on tension–pCa relationships relative to control (circles), whereas 5 μM C0C1m (squares; n = 4) significantly increased Ca2+ sensitivity of tension (ΔpCa50 = 0.27 ± 0.05).
Mentions: We next investigated whether the Ca2+-sensitizing effects of the motif required the presence of the flanking regions C1 or C2. We therefore generated protein constructs that combined the motif with one or the other of the flanking domains, i.e., C1m or mC2. As shown in Fig. 4 A, the C1m construct was effective at inducing a leftward shift of the force–pCa relationship, whereas mC2 at a comparable concentration failed to induce a leftward shift. Collectively, these results suggest that the motif plus C1, but not the motif plus C2, are necessary for the Ca2+-sensitizing effects of C1C2.

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