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Regulation of Bacterial Gene Activity Help (page 4)

By — McGraw-Hill Professional
Updated on Aug 23, 2011

Posttranslation Control

The expression of genes can be regulated after proteins have been synthesized (posttranslation control). Feedback inhibition (or end-product inhibition) is a regulatory mechanism involving inhibition of enzymatic activity. The end product of a synthetic pathway (usually a small molecule such as an amino acid) may combine loosely (if in high concentration) with the first enzyme in the pathway. This union does not occur at the catalytic site of the enzyme, but it does modify the tertiary or quaternary structures of the enzyme and hence inactivates the catalytic site. This allosteric transformation of the enzyme blocks its catalytic activity and prevents overproduction of the end product of the pathway and its intermediate metabolites.

EXAMPLE 10.10 The end product isoleucine in E. coli, when present in high concentration, unites with the first enzyme in its synthetic pathway and thus inhibits the entire pathway until isoleucine returns to normal levels through cellular consumption. Intermediates in the biosynthetic pathway are in numbered boxes; e = enzyme; g = gene.

Posttranslation Control

Practice problems for these concepts can be found at:

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