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Titolo:
EXCHANGE OF ATP FOR ADP ON HIGH-FORCE CROSS-BRIDGES OF SKINNED RABBITMUSCLE-FIBERS
Autore:
SEOW CY; FORD LE;
Indirizzi:
INDIANA UNIV,SCH MED,KRANNERT INST CARDIOL,1111 W 10 ST INDIANAPOLIS IN 46202 INDIANA UNIV,SCH MED,KRANNERT INST CARDIOL INDIANAPOLIS IN 46202
Titolo Testata:
Biophysical journal
fascicolo: 6, volume: 72, anno: 1997,
pagine: 2719 - 2735
SICI:
0006-3495(1997)72:6<2719:EOAFAO>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
SKELETAL-MUSCLE; FROG-MUSCLE; SHORTENING VELOCITY; FILAMENT OVERLAP; MYOSIN-FILAMENTS; PSOAS FIBERS; CAGED-ATP; CONTRACTION; TENSION; MGADP;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
50
Recensione:
Indirizzi per estratti:
Citazione:
C.Y. Seow e L.E. Ford, "EXCHANGE OF ATP FOR ADP ON HIGH-FORCE CROSS-BRIDGES OF SKINNED RABBITMUSCLE-FIBERS", Biophysical journal, 72(6), 1997, pp. 2719-2735

Abstract

The contractile properties of rabbit skinned muscle fibers were studied at 1-2 degrees C in different concentrations of MgATP and MgADP. Double-reciprocal plots of maximum velocity against MgATP concentration at different MgADP concentrations all extrapolated to the same value. This finding suggests that MgATP and MgADP compete for the same site on the cross-bridge, and that the exchange of MgATP for MgADP occurs without a detectable step intervening. The K-m for ATP was 0.32 mM. The K-i for MgADP was 0.33 mM. Control experiments suggested that the tortuosity of diffusion paths within the fibers reduced the radial diffusion coefficients for reactants about sixfold. Increasing MgADP from 0.18 to 2 mM at 5 mM ATP or lowering MgATP from 10 to 2 mM at 0.18 mM MgADP, respectively, increased isometric force by 25% and 23%, increased stiffness by 10% and 20%, and decreased maximum velocity by 35% and 31%. Two mechanisms appeared to be responsible. One detained bridges in high-force states, where they recovered from a length step with a slower time course. The other increased the fraction of attached bridges without altering the kinetics of their responses, possibly by an increased activation resulting from cooperative effects of the detained, high-force bridges. The rigor bridge was more effective than the ADP-bound bridge in increasing the number of attached bridges with unaltered kinetics.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 05/12/20 alle ore 00:27:05