Comparison of activities of recombinant eIF5A proteins and bovine testis eIF5A. The methionyl-puromycin synthesis assay was carried out as described under the section ‘Materials and methods’, using either [3H]methionyl-tRNA (A) or [35S]methionyl-tRNA (B) in two independent experiments. The dpm for [3H]methionyl-puromycin formed is twice that of [35S]methionyl-puromycin, since the specific radioactivity of [3H]methionyl-tRNA is approximately twice that of [35S]methionyl-tRNA. Abbreviations are: 5A(Lys), eIF5A(Lys); 5A(Dhp), eIF5A(Dhp); 5A(Hpu), eIF5A(Hpu); BT5A, bovine testis eIF5A.