Understanding Gene Regulation in Prokaryotes

Oct 11, 2024

Gene Regulation in Prokaryotes

Types of Genes

  • Constitutive Genes: Always active, often called housekeeping genes.
  • Facilitated Genes: Assist and help processes when needed.

Control Mechanisms in Prokaryotes

  • Goal: Efficient use of carbon and energy sources.
  • Levels of Control:
    1. Transcriptional Level (DNA Level): Proteins interact with promoters to regulate transcription.
    2. Post-transcriptional Events: If a gene is already transcribed, translation can be shut down.
    3. Post-translational Modifications: Degradation or modification of proteins to inhibit function.

Transcriptional Control

  • DNA Binding Proteins:
    • Function by interacting with DNA in a sequence-specific manner through molecular contacts, not specific base sequences.
    • Important Domains:
      • Zinc Finger
      • Leucine Zipper
      • Helix-Turn-Helix (emphasized for memorization)
    • Typically homodimeric: Two identical subunits; each polypeptide chain has a domain interacting with DNA sequences.

DNA Sequences and Binding

  • Inverted Repeat Sequences:
    • Specialized sequences present in the major groove of DNA.
    • Described as palindromic sequences (e.g., "race car").
    • Inversion allows for binding of each polypeptide in the dimer with each DNA strand.

Importance of these Mechanisms

  • Efficient regulation of transcription is crucial for cellular conservation of resources.
  • Many proteins discussed are DNA binding proteins, emphasizing their role in gene regulation.