pmoCAB

pmoCAB is the operon that encodes the subunits of the particulate methane monooxygenase (pMMO), the membrane-bound enzyme that catalyzes the first step of methane oxidation in aerobic methanotrophic bacteria. The enzyme converts methane to methanol using molecular oxygen, and copper is essential for its activity. pMMO operates in contrast to the soluble methane monooxygenase (sMMO), which is expressed under certain conditions.

The operon typically contains three genes, pmoC, pmoA, and pmoB, which encode the PmoC, PmoA, and PmoB protein subunits. These subunits assemble into the multimeric pMMO complex, which associates with intracytoplasmic membranes in methanotrophs. The exact stoichiometry and structure have been the subject of extensive structural and biochemical studies.

Expression of pmoCAB is regulated in part by copper availability. Under copper-replete conditions, pMMO is favored; under copper limitation, many methanotrophs induce sMMO encoded by mmoXYBZDC, enabling methane oxidation through a different active site.

pmoCAB is widespread among aerobic methanotrophs, including genera such as Methylococcus, Methylosinus, Methylomonas, and Methylomicrobium. The pmoA gene within the operon is commonly used as a molecular marker to detect and quantify methanotrophic bacteria in environmental DNA surveys.

Beyond ecology, pmoCAB and pMMO are areas of interest for understanding methane cycling and exploring potential biotechnological routes for methane valorization, though practical applications remain an area of ongoing research.