The three dimensional structure of the lysozyme from bacteriophage T4

Area of Science:

• Structural biology
• Biochemistry
• Molecular genetics

Background:

• Lysozymes are enzymes that degrade bacterial cell walls.
• Understanding enzyme structure is crucial for elucidating function and mechanism.
• Bacteriophage T4 lysozyme serves as a model system for studying enzyme structure-function relationships.

Purpose of the Study:

• To determine the three-dimensional structure of bacteriophage T4 lysozyme.
• To identify structural features potentially involved in catalytic activity.
• To compare the structure of T4 lysozyme with other known lysozymes.

Main Methods:

• X-ray crystallography
• Electron density map analysis at 2.5 A resolution
• Mutagenesis studies

Main Results:

• The structure reveals a polypeptide backbone folding into two lobes with a central cleft.
• Approximately 60% of the molecule adopts a helical conformation, with a region of antiparallel beta-structure.
• A catalytic cleft, deepening into a cavity, is identified, with side chains near its opening.
• Mutant T4 lysozymes with modifications near the cleft exhibit significantly reduced catalytic activity.

Conclusions:

• The determined three-dimensional structure of T4 phage lysozyme reveals distinct structural features.
• The cleft region is suggested to be catalytically important based on mutagenesis data.
• The structure of T4 lysozyme differs significantly from hen egg-white lysozyme, but the catalytic mechanisms remain to be fully elucidated.