Structural Analysis of CYP101C1 from Novosphingobium aromaticivorans DSM12444

CYP101C1 from Novosphingobium aromaticivorans DSM12444 is a homologue of CYP101D1 and CYP101D2 enzymes from the same bacterium and CYP101A1 from Pseudomonas putida. CYP101C1 does not bind camphor but is capable of binding and hydroxylating ionone derivatives including alpha- and beta-ionone and beta-damascone. The activity of CYP101C1 was highest with beta-damascone (k(cat)=86 s(-1)) but alpha-ionone oxidation was the most regioselective (98% at C3). The crystal structures of hexane-2,5-diol- and beta-ionone-bound CYP101C1 have been solved; both have open conformations and the hexanediol-bound form has a clear access channel from the heme to the bulk solvent. The entrance of this channel is blocked when beta-ionone binds to the enzyme. The heme moiety of CYP101C1 is in a significantly different environment compared to the other structurally characterised CYP101 enzymes. The likely ferredoxin binding site on the proximal face of CYP101C1 has a different topology but a similar overall positive charge compared to CYP101D1 and CYP101D2, all of which accept electrons from the ArR/Arx class I electron transfer system.