Protein Synthesis Lab Report

Protein synthesis

Introduction

Translation or protein synthesis is a central process of central dogma of molecular biology. It deals with production of proteins or chains of amino acids by making use of a mRNA as a template, ribosomes as protein synthesizing machinery and tRNA’s as carriers of amino acids during the translation process

Living cells devote about 90 % of their chemical energy to synthesis of proteins and only about 10 % to other biosynthetic processes. More than 35% of the dry weight of the cell consists of ribosomes, proteins involved in translation process and tRNA molecules. This suggests that protein synthesis is an important process for the survival of microorganisms

Protein synthesis process in

The components required for prokaryotic elongation process includes ,the initiation complex described above, aminoacyl-tRNAs, a set of three soluble cytosolic elongation factors (EF-Tu, EF-Ts, and EF-G in bacteria), and GTP.

During the first step of elongation cycle the next aminoacyl-tRNA binds to the ribosomal A site. The appropriate aminoacyl-tRNA associates with a complex of GTP-bound EF-Tu resulting in formation of aminoacyltRNA–EF-Tu–GTP complex. It binds to the ribosomal A site with simultaneous hydrolyzed of GTP and an EF-Tu–GDP complex is released from the 70S ribosome. The EF-Tu–GTP complex is then regenerated in a process requiring EF-Ts and GTP.

In the second step of the elongation cycle peptide bond formation takes place between the amino acids bound to the ribosomal P and A site by their respective t- RNA molecules. During this step the amino group of amioacid at the ribosomal A site acts as a nucleophile and displaces the tRNA in the Psite resulting in peptide bond formation between the 2 aminoacids. This results in formation of dipeptidyl t-RNA at the ribosomal A site and a deacylated tRNA at the ribosomal P site. The reaction is catalyzed by enzyme peptidyl transferase which is now known to be catalyzed by the ribosomal 23srRNA subunit of

This results in repositioning of the dipeptidyl tRNA to the ribosomal P site and the deacylated tRNA to the ribosomal E site, from where the tRNA is released into the cytosol. The reaction is catalyzed by enzyme translocase or EF-G in a reaction requiring energy from GTP hydrolysis. The 3 rd codon is now at ribosomal A site and the ribosomes are ready for the next elongation cycle. For each amino acid molecule added to the growing polypeptide chain 2 GTP molecules are hydrolyzed into GDP and