Structural determinants of cooperativity in acto-myosin interactions.

• Authors: Joanna Moraczewska
• Languages of publication: EN

Abstracts

EN

Regulation of muscle contraction is a very cooperative process. The presence of tropomyosin on the thin filament is both necessary and sufficient for cooperativity to occur. Data recently obtained with various tropomyosin isoforms and mutants help us to understand better the structural requirements in the thin filament for cooperative protein interactions. Forming an end-to-end overlap between neighboring tropomyosin molecules is not necessary for the cooperativity of the thin filament activation. When direct contacts between tropomyosin molecules are disrupted, the conformational changes in the filament are most probably transmitted cooperatively through actin subunits, although the exact nature of these changes is not known. The function of tropomyosin ends, alternatively expressed in various isoforms, is to confer specific actin affinity. Tropomyosin's affinity or actin is directly related to the size of the apparent cooperative unit defined as the number of actin subunits turned into the active state by binding of one myosin head. Inner sequences of tropomyosin, particularly actin-binding periods 3 to 5, play crucial role in myosin-induced activation of the thin filament. A plausible mechanism of tropomyosin function in this process is that inner tropomyosin regions are either specifically recognized by myosin or they define the right actin conformation required for tropomyosin movement from its blocking position.

Keywords

EN

cooperativity; acto-myosin regulation; tropomyosin; contraction

• Publisher: Polish Biochemical Society
• Journal: Acta Biochimica Polonica
• Year: 2002
• Volume: 49
• Issue: 4
• Pages: 805-812

Dates

published

2002

received

2002-10-22

revised

2002-11-12

accepted

2002-12-04

Contributors

author

Joanna Moraczewska

• Kazimierz Wielki University of Bydgoszcz, Institute of Biology and Environmental Protection, Bydgoszcz, and Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warszawa, Poland

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