Regulation of Prokaryotic gene expression
Regulation of Prokaryotic gene expression
Gene expression in bacteria is highly influenced by changing environment. Gene expression is regulated at several levels in bacteria:
- Transcription
- mRNA processing
- mRNA turnover
- Translation
- Post translational modification
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Constitutive Gene Expression
- Continuous expression of genes is called constitutive or housekeeping gene expression.
- Certain gene such as tRNA, rRNA, ribosomal protein, RNA polymerases, enzyme’s genes catalyzing metabolic reactions are continuously transcribed and translated to their final products because they are essential for living cells.
Regulatory Gene expression
- Genes expression that only takes place in response to certain external or internal signal are called regulatory gene expression.
- It is of two types on the basis of the types of signal to which they respond
Inducible gene expression
- Expression of genes which is induced by an environmental signal is called inducible gene expression.
- The gene is called inducible gene and the signal is termed as inducer.
- Genes of all the enzymes working in catabolic pathways are inducible in nature.
Repressible gene expression:
- When the expression of genes is suppressed by the signal present in the environment is called repressible gene expression and the gene is termed as repressible gene.
- The signal from environment which represses the gene expression is called co-repressor. Genes whose protein products (enzymes) working in anabolic (biosynthetic) pathway often are repressible.
- Both repression and induction occur at the transcription level.
Positive and Negative control of gene expression
- The regulation of gene expression—- induction (turning on) and repression (turning off) can occur by both positive control mechanism and negative control mechanism.
- Both the mechanisms involve the participation of regulatory genes.
- Genes that encode a protein which regulate the gene expression of other genes are called regulatory genes. This code for an activator or repressor that regulate the gene expression
- If genes are controlled by the presence of activator or co-activator protein than the mechanism is positive control mechanism.
- If genes are controlled by presence of repressor or co-repressor protein then the mechanism is negative control mechanism
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