Methanobactin

Methanobactin (mb) is a class of copper-binding and reducing chromophoric peptides initially identified in the methanotroph Methylococcus capsulatus Bath - and later in Methylosinus trichosporium OB3b - during the isolation of the membrane-associated or particulate methane monooxygenase (pMMO).

Methanobactin has an extremely high affinity for binding and Cu(I) with a Kd of approximately 1020 M−1 at pH 8.

OB3b is composed of 9 amino acid residues with two oxazolone rings, which take part in binding to copper ions.

Copper is bound and reduced at a tetradentate binding site composed of 2 oxazolone rings and 2 modified enethiol groups.

In 2010, it was suggested that mb OB3b is derived from a small, ribsomally-produced peptide precursor with the sequence of L-C-G-S-C-Y-P-C-S-C-M.[6] Functional mbOB3b is composed of (isobutyl group)-(Oxazolone ring A)-G-S-C-Y-(Oxazolone ring B)-S-M.[6] (Note that some specimens of mBOB3b are found without the C-terminal methionine and appear fully functional.)