N-formylmethionyl-sRNA as the initiator of protein synthesis.

Abstract
Several reasons for employing N-formylated aminoacyl-sRNA as a polypeptide chain initiator can be envisioned. The N-formylaminoacyl-sRNA may inherently define a direction for polypeptide growth on the ribosomal surface. This could be accomplished, for example, if the N-formyl bond mimicked the peptide bond and thus aided in the selection of one of the two proposed sRNA binding sites on the ribosome. Also, blocking the amino group of the first amino acid may facilitate the formation of the initial peptide bond by eliminating the positive charge on the amino group.