Figure 3. eIF4A binds eIF4G at two sites. In A, binding of full length eIF4A to the indicated eIF4G polypeptides in the Coomassie-stained SDS-PAGE gel (top panel) was determined following binding of the GST fusion proteins to glutathione Sepharose, resolution of bound eIF4A by SDS-PAGE, and its detection by Western analysis (bottom panel). GST was employed as a negative control. In B, summary of the eIF4A binding activity of eIF4G polypeptides. Strength of eIF4A binding is indicated by the number of pluses. -, Lack of eIF4A binding.