title: Crystal structures of cyclohexanone monooxygenase reveal complex domain movements and a sliding cofactor.
abstract: Cyclohexanone monooxygenase (CHMO) is a flavoprotein that carries out the archetypical Baeyer-Villiger oxidation of a variety of cyclic ketones into lactones. Using NADPH and O(2) as cosubstrates, the enzyme inserts one atom of oxygen into the substrate in a complex catalytic mechanism that involves the formation of a flavin-peroxide and Criegee intermediate. We present here the atomic structures of CHMO from an environmental Rhodococcus strain bound with FAD and NADP(+) in two distinct states, to resolutions of 2.3 and 2.2 A. The two conformations reveal domain shifts around multiple linkers and loop movements, involving conserved arginine 329 and tryptophan 492, which effect a translation of the nicotinamide resulting in a sliding cofactor. Consequently, the cofactor is ideally situated and subsequently repositioned during the catalytic cycle to first reduce the flavin and later stabilize formation of the Criegee intermediate. Concurrent movements of a loop adjacent to the active site demonstrate how this protein can effect large changes in the size and shape of the substrate binding pocket to accommodate a diverse range of substrates. Finally, the previously identified BVMO signature sequence is highlighted for its role in coordinating domain movements. Taken together, these structures provide mechanistic insights into CHMO-catalyzed Baeyer-Villiger oxidation.
authors.affiliation: Department of Biochemistry, McGill University, 3649 Prom Sir William Osler, Bellini Pavilion, Room 466, Montreal, QC, Canada H3G 0B1.
authors.forename: I Ahmad
authors.initials: IA
authors.lastname: Mirza
authors.forename: Brahm J
authors.initials: BJ
authors.lastname: Yachnin
authors.forename: Shaozhao
authors.initials: S
authors.lastname: Wang
authors.forename: Stephan
authors.initials: S
authors.lastname: Grosse
authors.forename: Hélène
authors.initials: H
authors.lastname: Bergeron
authors.forename: Akihiro
authors.initials: A
authors.lastname: Imura
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Iwaki
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Hasegawa
authors.forename: Peter C K
authors.initials: PC
authors.lastname: Lau
authors.forename: Albert M
authors.initials: AM
authors.lastname: Berghuis
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D009249:NADP / Q000737:chemistry / Q000378:metabolism*; D010105:Oxygenases / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012240:Rhodococcus / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D005182:Flavin-Adenine Dinucleotide; D009249:NADP; D010105:Oxygenases; C019961:cyclohexanone oxygenase