Abstract
AbstractParticulate methane monooxygenase (pMMO) is the main enzyme used by methanotrophic bacteria to metabolize methane as their sole source of carbon and energy. pMMO is a 300‐kDa copper‐dependent, membrane‐bound metalloenzyme housed in specialized intracytoplasmic membrane (ICM) structures formed under copper‐replete growth conditions. Five crystal structures of pMMO from different methanotrophic species have revealed that pMMO comprises three subunits, PmoA, PmoB, and PmoC, arranged in a (αβγ)3cylindrical‐shaped trimer. Since the last article, it has been established that pMMO contains two monocopper sites, one each in the PmoB and PmoC subunits. Both sites are likely involved in methane oxidation, but their specific roles are yet to be fully determined. The PmoD protein is unique to methanotrophs and is often encoded within the pMMO operon. PmoD consists of a single transmembrane helix and a cupredoxin‐like periplasmic domain that has been crystallographically characterized. Although its function remains unknown, disruption of the gene encoding PmoD results in a growth defect under high copper conditions, suggesting a potential role in methane oxidation. Biochemical analysis indicates that the periplasmic domain of PmoD binds copper, forming an unusual CuAsitein vitro.
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