I-protein, a new regulatory protein from vertebrate skeletal muscle. III. Function.
I-protein inhibited theMg-activated ATPase [EC 3.6.1.3] activity of actinomyosin by approximately 50% at low ionic strength. Concomitantly, the onset of superprecipitation was retarded. I-protein was found to bind to myosin, but not to F-actin. The inhibitory action of I-protein occurred only in the absence of Ca ions in the troponintropomyosin-actin myosin system. Addition of Ca ions abolished the effect. Thus, it is very likely that I-protein prevents unnecessary hydrolysis of ATP in the relaxed state of muscle.
D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D009124:Muscle Proteins / Q000378:metabolism*; D009126:Muscle Relaxation; D009218:Myosins / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D014336:Troponin / Q000378:metabolism
D000199:Actins; D046911:Macromolecular Substances; D009124:Muscle Proteins; D014336:Troponin; D011189:Potassium Chloride; D000205:Actomyosin; D000251:Adenosine Triphosphatases; D009218:Myosins; D002118:Calcium