Processing Polypeptide Chain

Processing Polypeptide Chain

Processing Polypeptide Chain - It has been seen that the starting amino acid in a polypeptide chain is either N-formylmethionine (prokaryotes) or methionine (eukaryotes). Many microorganisms, however, synthesize enzymes which catalyse cleavage of the formyl residue by a deformylase or of methionine by an amino peptidase from the polypeptide chain.

(1) Formyl methionyl peptide--->Formic acid + Methionyl peptide

(2) Methionyl peptide ---->Methionine + peptide

Thus the chain now begins with some other amino acid, particularly alanine, serine or threonine. Internal cleavages may also take place, e. g. the two cuts which break up the single proinsulin chain into the two pieces which constitute insulin. These two pieces are held together by S-S bonds.

In eukaryotes the polypeptide chain passes through a tunnel between the two ribosomal subunits into the cavity of the endoplasmic reticulum cisterna.

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Protein Synthesis Part 1 Release of Deacylated tRNA Hydrolysis of GTP Locking and Unlocking Ribosome Model inchworn Theory Conformational Changes Recognition of the Termination Signal Release of the Polypeptide Chain Prokaryote and Eukaryote Release Factors Processing Polypeptide Chain Rate of Protein Synthesis Signal Hypothesis Prokaryote and Eukaryote Protein Synthesis Teminism

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