Studies of the post-translational conversion of ribosomally encoded peptides to new natural products (RiPP pathways) have the potential to uncover many new enzyme functions. The prokaryotic redox cofactor pyrroloquinoline quinone (PQQ) belongs to a family of quino-cofactors that include the protein-derived structures of TPQ, LTQ, TTQ and CTQ. PQQ alone is formed from a ribosomally encoded <i>peptide</i> in a series of reactions that require C-C cross-linking, oxidative chemistry and proteolysis. The least understood gene product in this pathway, PqqB, has been probed via a series of metal reconstitution studies and small molecule binding assays, These probes, together with X-ray crystallographic characterization of enzyme-metal-analog complexes, suggest that the active substrate for PqqB is a peptide derived Tyr-Glu cross-linked intermediate. Possible catalytic roles for PqqB will be discussed and related to the established pathways for production of the protein-derived quino-cofactors.

Is PqqB, a protein of unknown function within the PQQ biosynthetic pathway, a novel copper enzyme?

254th National Meeting (2017)

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