Multiple Forms of Elongation Factor 1 from Calf Brain

Heavy and light forms of elongation factor 1 (EF-1) from calf brain have been partially purified. The heterogeneous heavy species (EF-1H) with molecular weights of 2.5 × 105to over 1 × 106appears to be a complex or aggregate of the light form of the enzyme (EF-1L); the latter has a molecular weight of between 50,000 and 60,000. EF-1Hbut not EF-1L, contains significant amounts of free and esterified cholesterol. Although EF-1Hand EF-1Lare both active in aminoacyl-tRNA binding to ribosomes, EF-1Lreacts with GTP and aminoacyl-tRNA more efficiently than EF-1H.