A mutation correcting the DNA interaction defects of a mutant phage lambda terminase, gpNu1 K35A terminase

Area of Science:

• Virology
• Molecular Biology
• Enzymology

Background:

• Bacteriophage lambda terminase is a heteromultimeric enzyme essential for DNA packaging.
• Terminase comprises gpNu1 and gpA subunits, each with a potential ATP-binding site.
• gpNu1 exhibits low-affinity ATPase activity stimulated by DNA; gpA has high-affinity ATPase.

Purpose of the Study:

• To investigate the role of the gpNu1 subunit in bacteriophage lambda DNA packaging.
• To identify mutations that suppress defects in DNA interaction and packaging caused by gpNu1 K35A.
• To characterize the functional impact of a novel suppressor mutation, A14V, in gpNu1.

Main Methods:

• Isolation and characterization of suppressor mutations for gpNu1 K35A defects.
• Biochemical assays to assess ATPase activity stimulation by DNA.
• Analysis of DNA packaging efficiency in the presence of mutations.

Main Results:

• A mutation, A14V, in the putative helix-turn-helix DNA binding domain of gpNu1 was identified.
• A14V suppresses the DNA-binding defects of gpNu1 K35A terminase.
• A14V restores normal DNA packaging, overcoming the lethality associated with gpNu1 K35A.

Conclusions:

• The A14V mutation in gpNu1 corrects DNA binding and packaging defects.
• This highlights the importance of specific residues in the gpNu1 DNA binding domain for terminase function.
• Understanding these interactions is crucial for bacteriophage DNA packaging mechanisms.