A Pseudomonas stutzeri outer membrane protein inserts copper into N2O reductase.

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Anaerobic respiration using N2O as an electron acceptor is vital for microbial life.
• N2O reductase (NosZ) is a key enzyme in this process, requiring copper for activity.
• Understanding the regulation and assembly of NosZ is crucial for microbial physiology.

Purpose of the Study:

• To investigate the genetic basis of inactive N2O reductase in specific mutant strains.
• To identify the role of a novel outer membrane protein, NosA, in N2O reductase function.

Main Methods:

• Induction of frameshift mutations using ICR-191.
• Analysis of N2O reductase activity and copper content in mutant strains.
• Identification and characterization of outer membrane proteins using SDS-PAGE.
• Copper sensitivity assays for mutant and parent strains.

Main Results:

• A class of mutants exhibited inactive N2O reductase lacking copper.
• These mutants failed to produce a 61,000-Mr outer membrane protein, NosA.
• NosA is not involved in copper uptake, as mutant and parent strains showed similar copper sensitivity.

Conclusions:

• NosA is essential for the functional assembly of N2O reductase.
• NosA likely plays a direct role in inserting copper into N2O reductase or maintaining its presence.
• This finding elucidates a critical step in the biogenesis of a key enzyme for anaerobic respiration.