80%) (fraction II). A detailed procedure for fraction II initiation factor preparation is described in this volume. 1 M KCI, 1 mM dithiothreitol, 50/aM EDTA, and 10% glycerol). 3 M KC1) in buffer D. Approximately 3-ml fractions are collected. 1 M KCI (fraction III). Figure 2 shows a typical DEAE-cellulose column elution pattern of different peptide chain initiation factor activities. [3'~S]Met-tRNAr binding activity was assayed both in the presence and in the absence of 5 mM Mg 2+ as described previously '9 (Fig.
2 mg of protein with a purity of 75-85%. General Discussion The 17 steps described above and shown in Fig. 1 lead to the purification of 8 initiation factors. The amounts of protein and specific activities at each step are given in Table I. Each of the preparations is analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Fig. 2). The purities, yields, and salt concentrations at which they are eluted from ion exchange columns are summarized in Table II, together with the number of different polypeptides per factor and their molecular weights.
Nucleic Acids and Protein Synthesis Part H by Kivie Moldave, Lawrence Grossman