ScienceAsia 1 (1975): 188-204 |doi: 10.2306/scienceasia1513-1874.1975.01.188

PRECISION OF INITIATION OF GLOBIN SYNTHESIS IN A RABBIT RETICULOCYTE CELL-FREE SYSTEM

PRAPON WILAIRAT,^a WILUAM R. WOODWARD^b and EDWARD HERBERT^b

Summary: The strictness of the requirement for Met-tRNA_F (the natural initiator tRNA) in the initiation of protein synthesis in eukaryotic cells has been examined by determining if N-blocked aminoacyl-tRNAs can force false initiation to occur when added to a cell-free protein synthesizing system.

          N-acetyl-¹⁴C-valyl-tRNA prepared by acetylation of rabbit reticulocyte valyl-tRNA was added to a cell-free system without perturbing its high efficiency in synthesizing hemoglobin and at a three-fold excess over the level of endogenous Met-tRNA_F. After one hour of incubation at 37^o, less than 0.2 % of-the added N-acetyl-valine had been transferred into N-terminal sites of completed globin chains. N-acetyl-¹⁴C-valyl-tRNA, nearly equal in amount to that of endogenous Met-tRNAF, could be recovered intact at the end of the incubation period. Similar results were obtained with N-acetylated aminoacyl-tRNA of leucine, serine, histidine and phenylalanine.

          In explaining these. results mechanisms involving inactivation of the N-acetylaminoacyl-tRNA during acetylation or during the incorporation experiment were considered and rejected in favor of one whereby the protein synthesizing apparatus is able to discriminate to a high degree against N-acetylated aminoacyl-tRNA

Download PDF

a Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok
b Department of Chemistry, University of Oregon, Eugene, Oregon 97403, U.S.A.

Received 20 June 1975