Molecular structure and function of bacterial nitric oxide reductase

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• Nitric oxide reductase (NOR) is vital for microbial respiration, catalyzing the reduction of nitric oxide (NO).
• Understanding the structure-function relationship of NOR is crucial for deciphering cellular respiration pathways.

Purpose of the Study:

• To determine the crystal structure of the membrane-integrated nitric oxide reductase (cNOR) from Pseudomonas aeruginosa.
• To elucidate the roles of conserved glutamate residues in the catalytic mechanism of cNOR.

Main Methods:

• X-ray crystallography was used to determine the high-resolution structure of cNOR.
• Structural analysis focused on identifying conserved residues and their potential roles in catalysis.

Main Results:

• The structure reveals the distinct NorC and NorB subunits, with heme c, heme b, and the binuclear center (heme b3 and non-heme Fe(B)) identified.
• Five conserved glutamate residues were analyzed: Glu211 and Glu280 act as proton donors, Glu215 influences the catalytic center's environment, and Glu135/Glu138 are involved in structural stability and proton transfer.

Conclusions:

• The solved structure provides insights into the molecular mechanism of NO reduction by cNOR.
• Specific glutamate residues are critical for catalysis and maintaining the protein's conformation for efficient electron-coupled proton transfer.