Purification and properties of a T4 bacteriophage factor that modifies valyl-tRNA synthetase of Escherichia coli

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• T4 bacteriophage infection alters host cell machinery.
• A phage-encoded peptide, tau, interacts with host valyl-transfer ribonucleic acid synthetase (EC 6.1.1.9).

Purpose of the Study:

• To investigate the in vitro interaction between purified tau peptide and valyl-tRNA synthetase.
• To characterize the physicochemical changes in the enzyme upon tau binding.

Main Methods:

• Rapid purification of tau peptide from T4-infected Escherichia coli.
• Sodium dodecyl sulfate-gel electrophoresis to determine tau peptide molecular weight.
• In vitro enzyme modification assays using purified tau and partially purified valyl-tRNA synthetase.

Main Results:

• Purified tau peptide (11,000 MW) converted partially purified valyl-tRNA synthetase to its viral-like form in vitro.
• The modified enzyme exhibited increased affinity for tRNA, similar to the enzyme from infected cells.
• Addition of tRNA or specific tRNAVal molecules increased the sedimentation rate of the modified enzyme.

Conclusions:

• The tau peptide directly modifies valyl-tRNA synthetase, altering its properties.
• This interaction is crucial for phage replication by altering host tRNA synthetase function.
• Amino acid analysis revealed high lysine and alanine content in tau, with absence of proline, tyrosine, phenylalanine, and methionine.