INHIBITION OF UNLOADED SHORTENING VELOCITY IN PERMEABILIZED MUSCLE-FIBERS BY CAGED-ATP COMPOUNDS

被引:29
作者
THIRLWELL, H
SLEEP, JA
FERENCZI, MA
机构
[1] NATL INST MED RES,LONDON NW7 1AA,ENGLAND
[2] UNIV LONDON KINGS COLL,RANDALL INST,LONDON WC2B 5RL,ENGLAND
关键词
D O I
10.1007/BF00122531
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
The effects of both the P-3-1-(2-nitrophenyl)ethyl ester of adenosine 5'-triphosphate (NPE-caged ATP) and its separate diastereoisomers, and the P-3-3',5'-dimethoxybenzoin ester of ATP (DMB-caged ATP) were studied on the unloaded shortening velocity of glycerinated rabbit psoas muscle fibres. The unloaded shortening velocities of the active fibres were measured as a function of ATP concentration (0.1-5 mM) using the 'slack-test' with and without 2 mM caged ATP. Shortening velocity followed a Michaelis-Menten relationship with ATP concentration, the K-m for ATP being 170 mu M. The caged ATP compounds inhibited shortening velocity, in a manner consistent with competitive inhibition, with a K-i of 1-2 mM. The R- and S-diastereoisomers of NPE-caged ATP showed the same degree of competitive inhibition of the shortening velocity, as did DMB-caged ATP. These observations suggest that caged ATP compounds bind to the ATPase site of the actomyosin where they compete with the substrate, Mg2+ ATP.
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页码:131 / 137
页数:7
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