Beta-Galactosidase Studies

4.

The lac Operon System

4.1.

Operon Structure and Organization

4.1.1.

Gene Arrangement

4.1.1.1.

4.1.1.2.

4.1.1.3.

4.1.2.

Regulatory Sequences

4.1.2.1.

Promoter Region

4.1.2.1.1.

RNA Polymerase Binding Site

4.1.2.1.2.

Transcription Start Site

4.1.2.2.

Operator Sequences

4.1.2.2.1.

Primary Operator

4.1.2.2.2.

Auxiliary Operators

4.1.2.3.

CAP-cAMP Binding Site

4.1.3.

Transcriptional Unit Boundaries

4.2.

Negative Regulation Mechanisms

4.2.1.

lac Repressor Protein

4.2.1.1.

lacI Gene Product

4.2.1.2.

Repressor Structure

4.2.1.2.1.

DNA-Binding Domain

4.2.1.2.2.

Allolactose-Binding Domain

4.2.1.3.

Repressor-Operator Interactions

4.2.2.

Induction Process

4.2.2.1.

Allolactose as Natural Inducer

4.2.2.2.

IPTG as Artificial Inducer

4.2.2.3.

Conformational Changes in Repressor

4.2.2.4.

Relief of Repression

4.2.3.

Basal Transcription Levels

4.3.

Positive Regulation Mechanisms

4.3.1.

Catabolite Repression

4.3.1.1.

Glucose Effect on Transcription

4.3.1.2.

cAMP Levels and Glucose Presence

4.3.2.

CAP-cAMP Complex

4.3.2.1.

Catabolite Activator Protein Structure

4.3.2.2.

cAMP Binding and Conformational Change

4.3.2.3.

DNA Binding Specificity

4.3.3.

Transcriptional Activation

4.3.3.1.

RNA Polymerase Recruitment

4.3.3.2.

Promoter Clearance Enhancement

4.4.

Integrated Regulation

4.4.1.

Combinatorial Control

4.4.2.

Growth Conditions and Expression Levels

4.4.2.1.

Glucose Present, Lactose Absent

4.4.2.2.

Glucose Present, Lactose Present

4.4.2.3.

Glucose Absent, Lactose Absent

4.4.2.4.

Glucose Absent, Lactose Present

4.4.3.

Diauxic Growth Phenomenon

4.4.4.

Physiological Advantages

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3. Catalytic Mechanism and Kinetics

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5. Biotechnological Applications