PmoC

PmoC, short for particulate methane monooxygenase subunit C, is a small integral membrane protein that forms part of the copper-dependent enzyme complex known as particulate methane monooxygenase (pMMO). It is encoded by the pmoC gene and is typically co-transcribed with pmoA and pmoB within the pmoCAB operon in aerobic methane-oxidizing bacteria.

PmoC's structure and localization are characteristic of its role as a membrane-embedded subunit. It is a hydrophobic protein predicted to contain multiple transmembrane helices and resides in the inner membrane where it associates with the larger subunits PmoA and PmoB to assemble the functional pMMO complex.

In terms of function, the catalytic activity of pMMO is largely attributed to the PmoA and PmoB subunits and their metal centers. PmoC is thought to contribute to the enzyme's structural integrity and assembly, and it may participate in electron transfer or copper handling within the complex. Across many methanotrophs, PmoC is typically required for proper pMMO activity, and alterations or deletions can impair enzyme function, underscoring its supportive but essential role.

Genetically, the pmoCAB operon is highly conserved among methane-oxidizing bacteria and is regulated by environmental factors such as methane availability and copper concentration. Under high copper conditions, pMMO is favored, whereas low copper can lead to the expression of the soluble methane monooxygenase. PmoC homologs are found in diverse pMMO-containing organisms, reflecting a conserved role in the membrane-bound enzyme complex.

Understanding PmoC contributes to a broader view of methane metabolism and has potential implications for biotechnological applications in methane bioconversion and bioremediation, as well as advancing knowledge of membrane-anchored multi-subunit monooxygenases.