Structural plasticity broadens the specificity of an engineered protease.

Area of Science:

• Enzymology
• Protein Engineering
• Structural Biology

Background:

• Alpha-lytic protease is a serine protease with a defined substrate specificity.
• Understanding enzyme active-site modifications is crucial for protein engineering.

Purpose of the Study:

• To investigate the impact of active-site mutation on alpha-lytic protease substrate specificity and activity.
• To elucidate the structural basis for altered substrate recognition.

Main Methods:

• Site-directed mutagenesis was used to replace an active-site methionine with alanine.
• Enzyme activity assays were performed to assess substrate specificity and catalytic efficiency.
• X-ray crystallography was employed to determine the structures of the wild-type and mutant proteases.

Main Results:

• The Met-to-Ala mutation in alpha-lytic protease resulted in a dramatic shift in substrate specificity.
• Both the primary mutant and a related mutant exhibited extraordinarily broad substrate specificity.
• X-ray crystallographic analysis revealed significant structural plasticity in the active site, including alternate side-chain conformations and binding-site flexibility.
• This plasticity allows for the effective accommodation of both large and small substrates.

Conclusions:

• Replacing an active-site methionine with alanine can drastically alter enzyme substrate specificity and enhance activity.
• Structural plasticity is a key determinant of broad substrate specificity in engineered enzymes.
• The findings provide insights into enzyme design and engineering for novel applications.