guanine nucleotide exchange factor ( gef ) activity in ribosomal high salt wash and cytosolic fractions from suckling ( 4-10-day-old ) and adult ( 60-day-old ) rats was assayed by two different methods , by measuring : ( i ) its ability to promote binding of [ 3h ] met-trnai to eukaryotic initiation factor-2 ( eif-2 ) preparations that are partially or wholly in the form of eif-2-gdp complexes ( at mg2+ concentrations near the optimum for protein synthesis ) , and ( ii ) under similar conditions , its ability to catalyze the displacement of [ 3h ] gdp , previously bound to eif-2 , by unlabelled gdp .
C0035553
ribosomal
C0597295
protein synthesis