The putative assembly factor CcoH is stably associated with the cbb3-type cytochrome oxidase

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Cytochrome c oxidases are vital for cellular respiration.
• cbb(3)-type cytochrome c oxidases (cbb(3)-Cox) are complex multisubunit enzymes.
• The biogenesis of cbb(3)-Cox involves distinct subcomplexes and accessory proteins.

Purpose of the Study:

• To elucidate the function of CcoH in cbb(3)-Cox assembly.
• To determine the role of CcoH in the formation of cbb(3)-Cox subcomplexes and the final active enzyme.
• To investigate the interaction of CcoH with cbb(3)-Cox components.

Main Methods:

• Analysis of cbb(3)-Cox assembly in the absence of CcoH.
• Chemical cross-linking to identify CcoH interaction partners.
• Site-directed mutagenesis to assess the role of CcoH domains.

Main Results:

• CcoH is essential for the formation of both cbb(3)-Cox subcomplexes (CcoQP, CcoNO) and the fully assembled enzyme.
• CcoH directly interacts with the CcoP subunit via its transmembrane domain.
• A C-terminal hydrophobic domain of CcoH is critical for merging subcomplexes into active cbb(3)-Cox.
• CcoH remains tightly associated with the mature cbb(3)-Cox complex.

Conclusions:

• CcoH functions as an integral subunit of cbb(3)-Cox, rather than a transient assembly factor.
• CcoH plays a dual role: facilitating subcomplex formation and mediating their final assembly.
• The findings redefine the understanding of cbb(3)-Cox biogenesis and the role of accessory proteins.