Concepts about translation.

Free online life science study material. Hi Here are some concepts about translation. (Procaryotes) Translation involves three organelles viz. Ribosome, mRNA and tRNA. Initiation, elongation and termination are three phases of translation. 1. Initiation: First step is tRNA charging. This takes place in cytosol. Amino acid(C group) + ATP(alpha phosphoryl group) aminoacylAMP +PPi Aminoacyl AMP +tRNA aminoacyl tRNA + AMP (enz. Aminoacyl tRNA synthase) PPi 2P (energy which drives reaction in forward direction). (tRNA is adaptor molecule as it carries anticodon and amino acid at 3’ end). • IF1, IF2 and IF3 are required as initiation factor. • Shine Dalgarno Sequence: Recognition site on mRNA, here smaller subunit of ribosome attach. It is complementary sequence of rRNA of smaller subunit. • IF1 comes and breaks the ribosome into its smaller and larger subunit(before translation). • IF3 binds to smaller subunit to prevent it from reuniting. • 30S, IF3 and mRNA is joined by GTP bound IF2 along with fmet-tRNAfmet. • The anticodon of this tRNA correctly pairs with mRNA’s initiation codon. • Ribosome has three sites A, P and E site. • P is only site where fmet can only bind rest amino acid bind at A site. • First amino acid fmet binds at P site with the help of IF2. • Smaller subunit, fmet, tRNA and mRNA comprise initiation complex. • Larger subunit then comes and binds to this complex and GTP is hydrolysed from IF2. • At this point all IFs depart. In the next blog I will cover initiation in eukaryotes.