An unusual role of tryptophan in PQQ-containing quinoproteins

Abstract

Methanol dehydrogenase is a bacterial quinoprotein containing PQQ at its active site, which is in the centre of a superbarrel structure made up of eight β-sheets arranged radially as the blades of a propeller. A series of novel tryptophan-docking interactions between the β-sheets make planar, stabilising girdles around the periphery of the protein. The tryptophan residues form stacking interactions, and hydrogen bonds through their indole ring NH groups.