Specificity of the initiator methionine tRNA for terminal and internal recognition

Abstract

Initiator methionyl-tRNA's from E. , coli and wheat embryo can also transfer methionine into internal positions of a polypeptide chain. This transfer depends on the protein synthesizing system used, an E. , coli system being about 10-times more active than a wheat embryo system. At low Mg 2+ concentration this incorporation depends on the presence of both initiation factors and fmet-tRNA f Met, but the rate is slower than that from met-tRNA m Met. Wheat embryo initiator met-tRNA 1 Met can initiate protein synthesis in an E. , coli system only when it is chemically formylated, but fmet-tRNA 2 Met (non-initiator) is inactive in this reaction.