14 november 2014

Today, 14 November 2014 . We have class in the evening with heavy rain outside. But today , all of us had lots of fun at Shah Alam. So we are so tired and sleepy in the class . ahaha. We continue our lecture in regulation of gene expression in bacteria. 

There are 2 modes of gene expression which are constitutive expression and inducible expression. Major modes of regulation is to control the activity of preexisting enzyme and control the amount of enzyme synthesized . Allosteric enzyme have 2 binding sites. Active site is substrate binds and allosteric site is inhibitor binds. In regulatory protein, binds DNA at promoter of regulated gene, the repressor block transcription and activator encourage transcription. In environmental sensor is small molecule and actives or inactivates regulatory protein.

Besides that, we also learn, Enzyme repression which is response to abundance of end-product and mediated by repressors. Corepressor controls enzyme synthesize. Inducible enzyme is enzyme synthesizes in the presence of inducer. Operon is a group of coordinately regulated structural genes with related metabolic functions and the promoter and operator sites that control their transcription. Promoter is the region of DNA where RNA polymerase initiates transcription. Operator is the region of DNA adjacent to structural gene that control their transcription.

If inducer absence, no mRNA synthesized and no enzymes. If trypotophan is present, the repressor becomes active and binds operator site. Inducer present the enzyme synthesis induced. If no lactose is available, no need enzyme to produce.

Happy Friday prof. :*