A myotrophic protein from chick embryo extract: Its purification, identity to transferrin, and indispensability for avian myogenesis☆

[摘要] Chickembyroextract(EE)hasbeenwidelyemployedasagrowth-promotingsupplementinavianmyogeniccellcultures.WehavepurifiedamyotrophicsubstancefromEEwithammoniumsulfateprecipitation,CM-SephadexandDEAE-cellulosechromatography.SaltgradientelutionfromDEAE-cellulosecolumnsyieldedthreeactivepeakswithaproteinof80Kdaltons.Theproteinshavedifferentisoelectricpointsof6.1,5.9,and5.7,respectively.TheypromotedchickmyoblaststoproliferateandmyotubestogrowwhenaddedintheplaceofEEtoabasalculturemedium(BCM)composedofEagle'sminimalessentialmediumandhorseserum.Theirmyotrophicactivitieswerethesameandreversiblylostbyremovalofprotein-boundFe.Theywereidentifiedastransferrin(Tf)speciesofdifferingnumbersofsialicacidresidues,onthebasisofphysicochemicalandimmunologicalanalyses.TfinEEconsistedofspeciesoffewersialicacidresiduesthanadultserumTf.IndispensabilityofFe-boundTfforEEtoexertmyotrophicactivitywasdemonstratedbyexperimentstoremoveTfbyimmunoprecipitationandtoremoveFefromTfinEE.Eithertreatmentledtoacompletelossofthemyotrophicactivity,whichwasrestoredbysupplementationofFe-boundTforFe3+.ComparisonofmyotrophicactivityofEEwiththatofTfindicatedthepresenceofotherfactorsinEEwhichpromotemyogeniccellgrowthsynergisticallywithTf.Fromtheresultsandonthebasisoftheclass-specificfunctionofTfonthecells,wediscusstherelationofTftonerve-derivedmyotrophicproteinsandotherfactorsinEE.

[学科分类] 生物科学（综合）