Cloning and sequence analysis of the gene encoding the DNA polymerase I from Mycobacterium tuberculosis

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The polA gene encodes DNA polymerase I, a crucial enzyme in DNA replication and repair.
• Understanding the enzymatic properties of DNA polymerase I from Mycobacterium tuberculosis is important for studying its role in the bacterium's biology.

Purpose of the Study:

• To clone and characterize the polA gene from Mycobacterium tuberculosis.
• To investigate the enzymatic activities of the encoded DNA polymerase I.

Main Methods:

• Cloning of the polA gene using PCR amplification and an internal gene segment probe.
• Sequence analysis to determine the polypeptide length and compare it with homologous sequences.
• Analysis of conserved motifs to predict enzymatic activities.

Main Results:

• The polA gene from Mycobacterium tuberculosis was successfully cloned.
• The gene encodes a 904-amino acid polypeptide with 89% identity to the Mycobacterium leprae homologue.
• The polypeptide contains structural elements for DNA polymerase and 5'-3' exonuclease activity.
• The polypeptide lacks motifs for 3'-5' exonuclease (proofreading) activity.

Conclusions:

• The Mycobacterium tuberculosis DNA polymerase I is structurally similar to its M. leprae counterpart.
• The enzyme possesses DNA polymerase and 5'-3' exonuclease activities.
• The absence of 3'-5' exonuclease activity suggests a unique role or regulation in Mycobacterium tuberculosis DNA metabolism.