7JVL

Structure of the M101A variant of the SidA ornithine hydroxylase complexed with NADP and the FAD in the "out" conformation

Summary for 7JVL

• Entry DOI: 10.2210/pdb7jvl/pdb
• Descriptor: L-ornithine N(5)-monooxygenase, FLAVIN-ADENINE DINUCLEOTIDE, NADP NICOTINAMIDE-ADENINE-DINUCLEOTIDE PHOSPHATE, ... (6 entities in total)
• Functional Keywords: flavin-containing monooxygenase, flavoprotein, oxidoreductase
• Biological source: Neosartorya fumigata
• Total number of polymer chains: 4
• Total formula weight: 234266.58

Authors

Tanner, J.J.,Campbell, A.C. (deposition date: 2020-08-21, release date: 2020-12-02, Last modification date: 2023-10-18)

Primary citation

Campbell, A.C.,Robinson, R.,Mena-Aguilar, D.,Sobrado, P.,Tanner, J.J.
Structural Determinants of Flavin Dynamics in a Class B Monooxygenase.
Biochemistry, 59:4609-4616, 2020

PubMed Abstract: The ornithine hydroxylase known as SidA is a class B flavin monooxygenase that catalyzes the first step in the biosynthesis of hydroxamate-containing siderophores in . Crystallographic studies of SidA revealed that the FAD undergoes dramatic conformational changes between and states during the catalytic cycle. We sought insight into the origins and purpose of flavin motion in class B monooxygenases by probing the function of Met101, a residue that contacts the pyrimidine ring of the FAD. Steady-state kinetic measurements showed that the mutant variant M101A has a 25-fold lower turnover number. Pre-steady-state kinetic measurements, pH profiles, and solvent kinetic isotope effect measurements were used to isolate the microscopic step that is responsible for the reduced steady-state activity. The data are consistent with a bottleneck in the final step of the mechanism, which involves flavin dehydration and the release of hydroxy-l-ornithine and NADP. Crystal structures were determined for M101A in the resting state and complexed with NADP. The resting enzyme structure is similar to that of wild-type SidA, consistent with M101A exhibiting normal kinetics for flavin reduction by NADPH and wild-type affinity for NADPH. In contrast, the structure of the M101A-NADP complex unexpectedly shows the FAD adopting the conformation and may represent a stalled conformation that is responsible for the slow kinetics. Altogether, our data support a previous proposal that one purpose of the FAD conformational change from to in class B flavin monooxygenases is to eject spent NADP in preparation for a new catalytic cycle.

PubMed: 33226785
DOI: 10.1021/acs.biochem.0c00783

Experimental method

X-RAY DIFFRACTION (2.1 Å)