1DWX

MURINE INDUCIBLE NITRIC OXIDE SYNTHASE OXYGENASE DIMER N-hydroxyarginine and tetrahydrobiopterin

Summary for 1DWX

• Entry DOI: 10.2210/pdb1dwx/pdb
• Related: 1DWV 1DWW 1NOC 1NOD 1NOS 1QOM 2NOD 2NOS 3NOD
• Descriptor: NITRIC OXIDE SYNTHASE, PROTOPORPHYRIN IX CONTAINING FE, 5,6,7,8-TETRAHYDROBIOPTERIN, ... (6 entities in total)
• Functional Keywords: oxidoreductase transferase complex, complex (oxidoreductase-transferase), nitric oxide monooxygenase, heme, dimer, intermediate, pterin, h4b, tetrahydrobiopterin, oxidoreductase-transferase complex, oxidoreductase/transferase
• Biological source: MUS MUSCULUS (MOUSE)
• Total number of polymer chains: 2
• Total formula weight: 99444.52

Authors

Crane, B.R.,Arvai, A.S.,Getzoff, E.D.,Stuehr, D.J.,Tainer, J.A. (deposition date: 1999-12-14, release date: 2000-02-06, Last modification date: 2024-05-08)

Primary citation

Crane, B.R.,Arvai, A.S.,Ghosh, S.,Getzoff, E.D.,Stuehr, D.J.,Tainer, J.A.
Structures of the N(Omega)-Hydroxy-L-Arginine Complex of Inducible Nitric Oxide Synthase Oxygenase Dimer with Active Andinactive Pterins
Biochemistry, 39:4608-, 2000

PubMed Abstract: Nitric oxide synthases (NOSs) catalyze two mechanistically distinct, tetrahydrobiopterin (H(4)B)-dependent, heme-based oxidations that first convert L-arginine (L-Arg) to N(omega)-hydroxy-L-arginine (NHA) and then NHA to L-citrulline and nitric oxide. Structures of the murine inducible NOS oxygenase domain (iNOS(ox)) complexed with NHA indicate that NHA and L-Arg both bind with the same conformation adjacent to the heme iron and neither interacts directly with it nor with H(4)B. Steric restriction of dioxygen binding to the heme in the NHA complex suggests either small conformational adjustments in the ternary complex or a concerted reaction of dioxygen with NHA and the heme iron. Interactions of the NHA hydroxyl with active center beta-structure and the heme ring polarize and distort the hydroxyguanidinium to increase substrate reactivity. Steric constraints in the active center rule against superoxo-iron accepting a hydrogen atom from the NHA hydroxyl in their initial reaction, but support an Fe(III)-peroxo-NHA radical conjugate as an intermediate. However, our structures do not exclude an oxo-iron intermediate participating in either L-Arg or NHA oxidation. Identical binding modes for active H(4)B, the inactive quinonoid-dihydrobiopterin (q-H(2)B), and inactive 4-amino-H(4)B indicate that conformational differences cannot explain pterin inactivity. Different redox and/or protonation states of q-H(2)B and 4-amino-H(4)B relative to H(4)B likely affect their ability to electronically influence the heme and/or undergo redox reactions during NOS catalysis. On the basis of these structures, we propose a testable mechanism where neutral H(4)B transfers both an electron and a 3,4-amide proton to the heme during the first step of NO synthesis.

PubMed: 10769116
DOI: 10.1021/BI992409A

Experimental method

X-RAY DIFFRACTION (2.6 Å)