Polypeptide chain initiation regulation

Clemens, M. J., 1976, Functional relationships between reticulocyte polypeptide chain initiation factor (IF-MP) and the translational inhibitor involved in regulation of protein synthesis by haemin, Eur. J. Biochem. 66 413. 

Pain, V. M., Lewis, J. A., Huvos, P., Henshaw, E. C., and Clemens, M. J., 1980, The effects of amino acid starvation on regulation of polypeptide chain initiation in Ehrlich ascites tumor cells, J. Biol. Chem. 255 1486. 

At the ribosome, which travels along the mRNA, the tRNA molecule is bound such that its anticodon can interact with a nucleotide triplet on mRNA (the codon). If the anticodon is complementary to a codon triplet on the mRNA, the amino acid attached at the 3 -terminus of the tRNA is transferred to the amino terminus of the growing polypeptide chain if it is not complementanty, the tRNA is rejected and another one is checked for complementary. The whole process is repeated until the synthesis of the protein is completed. It is initiated, as well as terminated, by specific codons regulating this translation. 

The activity of a target gene product can also be modulated at the post-transcriptional level by adjusting the efficiency at which mRNA is translated into a polypeptide chain. Translation is conceptually divided into four phases initiation, elongation, termination, and ribosome recycling [163]. Regulation of... 

In this situation, two different polypeptide chains interact to form a new specific complex, whose biologic activity can be modified by ligands that bind to the precursor subunits. This type of regulation has been extensively studied for the aspartate transcarbamylase of E. coli (Gerhart, 1970). This enzyme catalyzed the initial step in the synthesis of cytidine nucleotides it is allosterically inhibited by CTP and shows positive cooperativity for substrate. It may be dissociated by mercurials into catalytic subunits, which are insensitive to CTP and which exhibit hyperbolic kinetics for substrate, and into regulatory subunits which bind CTP. 

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