Structure-activity correlations in pentachlorobenzene oxidation by engineered cytochrome P450cam

Area of Science:

• Biochemistry
• Structural Biology
• Environmental Science

Background:

• Cytochrome P450 enzymes are crucial for metabolizing diverse compounds.
• Pentachlorobenzene (PeCB) is a persistent environmental pollutant requiring bioremediation strategies.
• Engineering P450cam for enhanced PeCB oxidation is vital for environmental cleanup.

Purpose of the Study:

• To elucidate the structural basis of engineered P450cam's interaction with pentachlorobenzene (PeCB).
• To understand how specific mutations influence substrate binding and catalytic activity.
• To further optimize P450cam for efficient oxidation of recalcitrant pollutants.

Main Methods:

• Crystallography was used to determine the structure of a 4-mutant P450cam and its complex with PeCB.
• Site-directed mutagenesis was employed to introduce new mutations (T101A) based on structural insights.
• Enzyme activity assays were performed to quantify PeCB oxidation by engineered mutants.

Main Results:

• The crystal structure revealed PeCB binding face-on to the heme, with a key chlorine atom interacting with the cavity created by the L244A mutation.
• The oxygen-binding groove exhibited flexibility, accommodating mutations without compromising enzyme activity.
• A T101A mutation enhanced substrate reorientation, resulting in a 5-mutant with 3-fold higher PeCB oxidation activity compared to the 4-mutant.

Conclusions:

• Structural insights into P450cam-PeCB interactions guided rational enzyme engineering.
• Mutations L244A and T101A are critical for enhancing PeCB binding and catalytic efficiency.
• Engineered P450cam variants show significant potential for the bioremediation of persistent organic pollutants like PeCB.