Turnover of myosin heavy and light chains in cultured embryonic chick cardiac and skeletal muscle☆

[摘要] Therelativeratesofsynthesisandbreakdownofmyosinheavyandlightchainswerestudiedinprimarycellculturesofembryonicchickcardiacandskeletalmuscle.Measurementsweremadeafter4daysinculture,atwhichtimebothskeletalandcardiacculturesweredifferentiatedandcontractedspontaneously.Followinga4-hrpulseofradioactiveleucine,myosinanditsheavyandlightchainswereextractedto90%orgreaterpurityandthespecificactivitiesoftheproteinsweredetermined.Incardiacmuscle,myosinheavychainsweresynthesizedapproximately1.6timestherateofmyosinlightchains,andinskeletalmuscle,heavychainsweresynthesizedatapproximately1.4timestherateoflightchains.Relativeratesofdegradationofmuscleproteinsweredeterminedusingadual-isotopetechnique.Ingeneral,thesolubleandmyofibrillarproteinsofbothtypesofmusclehaddecayratesproportionaltotheirmolecularweights(largerproteinsgenerallyhadhigherdecayrates)basedonanalysesutilizingsodiumdodecylsulfate-polyacrylamidegelelectrophoresis.Anotableexceptiontothisgeneralrulewasmyosinheavychains,whichhaddecayratesonlyslightlyhigherthanthemyosinlightchains.Directmeasurementsonpurifiedproteinsindicatedthattheheavychainsofmyosinwereturningoverataslightlygreaterrate(approximately20%)thanthemyosinlightchainsinbothcardiacandskeletalmuscle.Thereasonsfortheapparentdiscrepancybetweenthesemeasurementsofmyosinheavyandlightchainsynthesisanddegradationarediscussed.

[学科分类] 生物科学（综合）