Characterization of the role of copCD in copper uptake and the “copper-switch” in Methylosinus trichosporium OB3b

<span class="paragraphSection"><div class="boxTitle">Abstract</div>Methanotrophs, or methane-oxidizing bacteria exhibit a unique 'copper-switch' where expression of two forms of methane monooxygenase is controlled by the availability of copper. In the absence of copper, a cytoplasmic or soluble methane monooxygenase (sMMO) is expressed. In the presence of copper a membrane-bound or particulate methane monooxygenase (pMMO) is expressed. These two forms of MMO have very different properties, and elucidation of the basis of the copper-switch is of significant interest as methanotrophs are becoming increasingly popular for the valorization of methane. Recently it was suggested via characterization of a mutant of <span style="font-style:italic;">Methylosinus trichosporium</span> OB3b that expresses sMMO in the presence of copper (smmoC mutant) that the copper-switch may be based on <span style="font-style:italic;">copCD.</span> These genes encode for a periplasmic copper-binding protein and an inner membrane protein, respectively, and are used by other bacteria for copper uptake. Specific knockouts of <span style="font-style:italic;">copCD</span> in <span style="font-style:italic;">M. trichosporium</span> OB3b wildtype, however, show these genes are not part of the copper-switch in methanotrophs, nor do they appear to be critical for copper uptake. Rather, it appears that the constitutive expression of sMMO in the smmoC mutant of <span style="font-style:italic;">M. trichosporium</span> OB3b may be due to multiple lesions as smmoC was generated via random chemical mutagenesis.</span>

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