Initiation of the alpha chain of rabbit hemoglobin.

Abstract

The first step in the synthesis of all proteins in E. coli is the binding of N-formyl-methionine tRNA to a complex formed between a 30 S ribosome and a mRNA molecule (Nomura and Lowry, 1967). The N-formyl-methionine initiates the synthesis of the protein, becoming incorporated at the amino terminal end of the growing polypeptide chains (Capecchi, 1966). At some point in the synthesis of each protein either the formyl group or the formyl group and the methionine residue are cleaved off to expose the amino terminal residue of the finished protein. We made the assumption that the mechanism of chain initiation in mammalian cells would also result in the transient incorporation of an initiator molecule at the amino terminal position of the growing polypeptide chains. We decided to check on this assumption by studying the synthesis of the α chain of hemoglobin in rabbit reticulocytes. This system has two advantages:...