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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

Schematic diagram of the apparatus used to obtain force measurements and original chart recordings. (Top, inset) Attachment method for securing a permeabilized trabecula to metal troughs. One trough was attached to the active end of a force transducer and the other to a motor for rapid changes in length. (Bottom) Original chart records showing Ca2+-activated force in the presence and absence of 5 μM C1C2 or 10 μM C0C1. The pCa values are shown above each activation, and the presence of C1C2 or C0C1 in bath solutions is indicated by bars.
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fig2: Schematic diagram of the apparatus used to obtain force measurements and original chart recordings. (Top, inset) Attachment method for securing a permeabilized trabecula to metal troughs. One trough was attached to the active end of a force transducer and the other to a motor for rapid changes in length. (Bottom) Original chart records showing Ca2+-activated force in the presence and absence of 5 μM C1C2 or 10 μM C0C1. The pCa values are shown above each activation, and the presence of C1C2 or C0C1 in bath solutions is indicated by bars.

Mentions: The apparatus for force measurements is shown schematically in Fig. 2. Permeabilized trabeculae were transferred from a glass Petri dish to a temperature-controlled stainless steel plate containing six experimental chambers (Aurora Scientific Inc.). The first chamber contained relaxing solution and was large enough to facilitate mounting of a trabecula between a force transducer (model 400A; Aurora Scientific Inc.) and a torque motor (model 312C; Aurora Scientific Inc.) for rapid adjustments of fiber length. Trabeculae were secured to the force transducer and motor as shown in Fig. 2 by placing each end of a trabecula into a trough constructed from a bisected 25-gauge needle. The ends of the trabecula were then overlayed with a segment (∼1 mm in length) of 4.0 suture material. The suture and trabecula were next secured to the trough by tying with a strand of unwaxed dental floss (approximately equivalent to 10.0 suture thread). After securing each end of the trabecula, the entire stainless steel plate containing the experimental wells and the trabecula was placed on the stage of an inverted microscope (IX71; Olympus) fitted with a 12–mega pixel digital camera (DP70; Olympus) for visualization of the trabecula and measurement of fiber dimensions and sarcomere length. Sarcomere length was adjusted to ∼2.3 μm in relaxing solution and monitored throughout the course of an experiment.


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)

Schematic diagram of the apparatus used to obtain force measurements and original chart recordings. (Top, inset) Attachment method for securing a permeabilized trabecula to metal troughs. One trough was attached to the active end of a force transducer and the other to a motor for rapid changes in length. (Bottom) Original chart records showing Ca2+-activated force in the presence and absence of 5 μM C1C2 or 10 μM C0C1. The pCa values are shown above each activation, and the presence of C1C2 or C0C1 in bath solutions is indicated by bars.
© Copyright Policy
Related In: Results  -  Collection

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

fig2: Schematic diagram of the apparatus used to obtain force measurements and original chart recordings. (Top, inset) Attachment method for securing a permeabilized trabecula to metal troughs. One trough was attached to the active end of a force transducer and the other to a motor for rapid changes in length. (Bottom) Original chart records showing Ca2+-activated force in the presence and absence of 5 μM C1C2 or 10 μM C0C1. The pCa values are shown above each activation, and the presence of C1C2 or C0C1 in bath solutions is indicated by bars.
Mentions: The apparatus for force measurements is shown schematically in Fig. 2. Permeabilized trabeculae were transferred from a glass Petri dish to a temperature-controlled stainless steel plate containing six experimental chambers (Aurora Scientific Inc.). The first chamber contained relaxing solution and was large enough to facilitate mounting of a trabecula between a force transducer (model 400A; Aurora Scientific Inc.) and a torque motor (model 312C; Aurora Scientific Inc.) for rapid adjustments of fiber length. Trabeculae were secured to the force transducer and motor as shown in Fig. 2 by placing each end of a trabecula into a trough constructed from a bisected 25-gauge needle. The ends of the trabecula were then overlayed with a segment (∼1 mm in length) of 4.0 suture material. The suture and trabecula were next secured to the trough by tying with a strand of unwaxed dental floss (approximately equivalent to 10.0 suture thread). After securing each end of the trabecula, the entire stainless steel plate containing the experimental wells and the trabecula was placed on the stage of an inverted microscope (IX71; Olympus) fitted with a 12–mega pixel digital camera (DP70; Olympus) for visualization of the trabecula and measurement of fiber dimensions and sarcomere length. Sarcomere length was adjusted to ∼2.3 μm in relaxing solution and monitored throughout the course of an experiment.

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