lec.3&4.prok_trxn_control

lec.3&4.prok_trxn_control - Regulation of...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Regulation of prokaryotic transcription 1. Single-celled organisms with short doubling times must respond extremely rapidly to their environment. 2. Half-life of most mRNAs is short (on the order of a few minutes). 1. Coupled transcription and translation occur in a single cellular compartment. Therefore, transcriptional initiation is usually the major control point. Most prokaryotic genes are regulated in units called operons (Jacob and Monod, 1960) Operon: a coordinated unit of gene expression consisting of one or more related genes and the operator and promoter sequences that regulate their transcription. The mRNAs thus produced are “polycistronic’—multiple genes on a single transcript.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
The metabolism of lactose in E. coli To use lactose as an energy source, cells must contain the enzyme β -galactosidase. Utilization of lactose also requires the enzyme lactose permease to transport lactose into the cell. Expression of these enzymes is rapidly induced ~1000-fold when cells are grown in lactose compared to glucose. QuickTimeª and a GIF decompressor are needed to see this picture. IPTG: non- metabolizable artificial inducer (can’t be cleaved) Trans- glycosylation LacZ: β -galactosidase; Y: galactoside permease; A: transacetylase (function unknown). P: promoter; O: operator. LacI: repressor; P I and LacI are not part of the operon.
Background image of page 2
Negative regulation of the lac operon Negative regulation: The product of the I gene, the repressor, blocks the expression of the Z, Y, and A genes by interacting with the operator (O) . The inducer (lactose or IPTG)
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 18

lec.3&4.prok_trxn_control - Regulation of...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online