Temperature-Dependence of Isometric Tension and Cross-Bridge Kinetics of Cardiac Muscle Fibers Reconstituted with a Tropomyosin Internal Deletion Mutant

Xiaoying Lu; Larry S Tobacman; Masataka Kawai

doi:10.1529/biophysj.106.084608

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Temperature-Dependence of Isometric Tension and Cross-Bridge Kinetics of Cardiac Muscle Fibers Reconstituted with a Tropomyosin Internal Deletion Mutant

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Temperature-Dependence of Isometric Tension and Cross-Bridge Kinetics of Cardiac Muscle Fibers Reconstituted with a Tropomyosin Internal Deletion Mutant

Xiaoying Lu, Larry S Tobacman and Masataka Kawai

Biophysical journal, Vol.91(11), pp.4230-4240

12/01/2006

DOI: 10.1529/biophysj.106.084608

PMCID: PMC1635655

PMID: 16980359

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Abstract

The effect of temperature on isometric tension and cross-bridge kinetics was studied with a tropomyosin (Tm) internal deletion mutant AS-Δ23Tm (Ala-Ser-Tm Δ(47–123)) in bovine cardiac muscle fibers by using the thin filament extraction and reconstitution technique. The results are compared with those from actin reconstituted alone, cardiac muscle-derived control acetyl-Tm, and recombinant control AS-Tm. In all four reconstituted muscle groups, isometric tension and stiffness increased linearly with temperature in the range 5–40°C for fibers activated in the presence of saturating ATP and Ca 2+ . The slopes of the temperature-tension plots of the two controls were very similar, whereas the slope derived from fibers with actin alone had ∼40% the control value, and the slope from mutant Tm had ∼36% the control value. Sinusoidal analysis was performed to study the temperature dependence of cross-bridge kinetics. All three exponential processes A, B, and C were identified in the high temperature range (30–40°C); only processes B and C were identified in the mid-temperature range (15–25°C), and only process C was identified in the low temperature range (5–10°C). At a given temperature, similar apparent rate constants (2 π a, 2 π b, 2 π c) were observed in all four muscle groups, whereas their magnitudes were markedly less in the order of AS-Δ23Tm < Actin < AS-Tm ≈ Acetyl-Tm groups. Our observations are consistent with the hypothesis that Tm enhances hydrophobic and stereospecific interactions (positive allosteric effect) between actin and myosin, but Δ23Tm decreases these interactions (negative allosteric effect). Our observations further indicate that tension/cross-bridge is increased by Tm, but is diminished by Δ23Tm. We conclude that Tm affects the conformation of actin so as to increase the area of hydrophobic interaction between actin and myosin molecules.

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Title: Subtitle: Temperature-Dependence of Isometric Tension and Cross-Bridge Kinetics of Cardiac Muscle Fibers Reconstituted with a Tropomyosin Internal Deletion Mutant
Creators: Xiaoying Lu - Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa; and
Larry S Tobacman - Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa; and
Masataka Kawai - Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa; and
Resource Type: Journal article
Publication Details: Biophysical journal, Vol.91(11), pp.4230-4240
Publisher: Biophysical Society
DOI: 10.1529/biophysj.106.084608
PMID: 16980359
PMCID: PMC1635655
ISSN: 0006-3495
eISSN: 1542-0086
Grant note: DOI: 10.13039/100000968, name: American Heart Association, award: 0320083Z, 0520084Z; DOI: 10.13039/100000002, name: National Institutes of Health, award: HL038834, HL70041
Language: English
Date published: 12/01/2006
Academic Unit: Anatomy and Cell Biology; Internal Medicine
Record Identifier: 9984025588402771

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