Molecular cloning and expression of cDNA for mammalian translation initiation factor 5.

Eukaryotic translation initiation factor 5 (eIF-5) catalyzes the hydrolysis of GTP bound to the 40S ribosomal initiation complex (40S.AUG.Met-tRNAf-eIF-2.GTP) with the subsequent joining of a 60S ribosomal subunit resulting in the formation of a functional 80S initiation complex. A rat cDNA that encodes eIF-5 has been isolated and expressed in Escherichia coli to yield a catalytically active eIF-5 protein. The 3.55-kb cDNA encodes a protein of 429 amino acids (calculated M(r) 48,926) with properties that are similar to eIF-5 isolated from rabbit reticulocyte lysates. The deduced amino acid sequence of eIF-5 contains sequence motifs characteristic of proteins of the GTPase superfamily.