The initiation of protein synthesis requires the eukaryotic translation initiation factor (eIF) 2, which uses energy from the hydrolysis of GTP. Another factor, eIF5, accelerates the GTP-hydrolysing activity of eIF2. Here, two other roles for eIF5 have been defined. One involves stabilizing GDP, the product of GTP hydrolysis, on eIF2. In its other role, eIF5 works with phosphorylated eIF2 to inhibit the guanine-nucleotide exchange factor eIF2B. These results clarify our understanding of how the initiation of translation is regulated.
- Martin D. Jennings
- Graham D. Pavitt
