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-1(H)) with molecular weights of 2.5 x 10(5) to over 1 x 10(6) appears to be a complex or aggregate of the light form of the enzyme (EF-1(L)); the latter has a molecular weight of between 50,000 and 60,000. EF-1(H) but not EF-1(L), contains significant amounts of free and esterified cholesterol. Although EF-1(H) and EF-1(L) are both active in aminoacyl-tRNA binding to ribosomes, EF-1(L) reacts with GTP and aminoacyl-tRNA more efficiently than EF-1(H).