The type II quinohemoprotein alcohol dehydrogenase of Pseudomonas putida is a periplasmic enzyme that oxidizes substrate alcohols to the aldehyde and transfers electrons first to pyrroloquinoline quinone (PQQ) and then to an internal heme group. The 1.9 Angstrom resolution crystal structure reveals that the enzyme contains a large N-terminal eight-stranded beta propeller domain (similar to60 kDa) similar to methanol dehydrogenase and a small C-terminal c-type cytochrome domain (similar to10 kDa) similar to the cytochrome subunit of p-cresol methylhydoxylase. The PQQ is bound near the axis of the propeller domain about 14 Angstrom from the heme. A molecule of acetone, the product of the oxidation of isopropanol present during crystallization, appears to be bound in the active site cavity.