Repressor (redirected from Repressors)

repressor: see nucleic acid.

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repressor [ri′pres·ər]

(biochemistry)

An end product of metabolism which represses the synthesis of enzymes in the metabolic pathway.

(genetics)

The product of a regulator gene that acts to repress the transcription of another gene.

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Repressor 

a special regulating protein formed in bacterial cells that halts transcription, which is the synthesis of messenger ribonucleic acid (m-RNA) from a specific operon (a group of genes that carry out the synthesis of functionally related enzymes). The number of different repressors corresponds to the number of operons.

Unlike other proteins, a repressor present in a cell consists of ten to 20 molecules. The synthesis of m-RNA ceases when a repressor combines with an operator, which is the regulating part of an operon. An effector, for example, lactose in a lactose operon, interacts with a repressor to form a complex that inactivates and produces a reversible spatial change in a repressor molecule. This type of repressor can no longer combine with an operator and, as a result, m-RNA synthesis resumes.