Universität zu Köln

Stehle, Robert and Tesi, Chiara (2017). Kinetic coupling of phosphate release, force generation and rate-limiting steps in the cross-bridge cycle. J. Muscle Res. Cell Motil., 38 (3-4). S. 275 - 290. DORDRECHT: SPRINGER. ISSN 1573-2657

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Abstract

A basic goal in muscle research is to understand how the cyclic ATPase activity of cross-bridges is converted into mechanical force. A direct approach to study the chemo-mechanical coupling between P-i release and the force-generating step is provided by the kinetics of force response induced by a rapid change in [P-i]. Classical studies on fibres using caged-P-i discovered that rapid increases in [P-i] induce fast force decays dependent on final [P-i] whose kinetics were interpreted to probe a fast force-generating step prior to P-i release. However, this hypothesis was called into question by studies on skeletal and cardiac myofibrils subjected to P-i jumps in both directions (increases and decreases in [P-i]) which revealed that rapid decreases in [P-i] trigger force rises with slow kinetics, similar to those of calcium-induced force development and mechanically-induced force redevelopment at the same [P-i]. A possible explanation for this discrepancy came from imaging of individual sarcomeres in cardiac myofibrils, showing that the fast force decay upon increase in [P-i] results from so-called sarcomere 'give'. The slow force rise upon decrease in [P-i] was found to better reflect overall sarcomeres cross-bridge kinetics and its [P-i] dependence, suggesting that the force generation coupled to P-i release cannot be separated from the rate-limiting transition. The reasons for the different conclusions achieved in fibre and myofibril studies are re-examined as the recent findings on cardiac myofibrils have fundamental consequences for the coupling between P-i release, rate-limiting steps and force generation. The implications from P-i-induced force kinetics of myofibrils are discussed in combination with historical and recent models of the cross-bridge cycle.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Stehle, Robert UNSPECIFIED UNSPECIFIED UNSPECIFIED Tesi, Chiara UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-222113
DOI:	10.1007/s10974-017-9482-8
Journal or Publication Title:	J. Muscle Res. Cell Motil.
Volume:	38
Number:	3-4
Page Range:	S. 275 - 290
Date:	2017
Publisher:	SPRINGER
Place of Publication:	DORDRECHT
ISSN:	1573-2657
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SKELETAL-MUSCLE FIBERS; RABBIT PSOAS MUSCLE; ACTOMYOSIN ATPASE ACTIVITY; MYOSIN POWER STROKE; INORGANIC-PHOSPHATE; SARCOMERE DYNAMICS; SKINNED FIBERS; STRIATED-MUSCLE; SINGLE MYOFIBRILS; CARDIAC-MUSCLE Multiple languages Cell Biology Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/22211