2CA3

Sulfite dehydrogenase from Starkeya Novella r55m mutant

2CA3 の概要

• エントリーDOI: 10.2210/pdb2ca3/pdb
• 関連するPDBエントリー: 2BLF 2BPB 2C9X
• 分子名称: SULFITE\:CYTOCHROME C OXIDOREDUCTASE SUBUNIT A, SULFITE\:CYTOCHROME C OXIDOREDUCTASE SUBUNIT B, (MOLYBDOPTERIN-S,S)-OXO-MOLYBDENUM, ... (6 entities in total)
• 機能のキーワード: sulfite oxidase, molybdopterin, c-type cytochrome, heme, mutant, oxidoreductase
• 由来する生物種: THIOBACILLUS NOVELLUS; 詳細
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 50329.46

構造登録者

Bailey, S.,Kappler, U.,Feng, C.,Honeychurch, M.J.,Bernhardt, P.V.,Tollin, G.,Enemark, J.H. (登録日: 2005-12-16, 公開日: 2007-02-20, 最終更新日: 2024-10-16)

主引用文献

Bailey, S.,Rapson, T.,Johnson-Winters, K.,Astashkin, A.V.,Enemark, J.H.,Kappler, U.
Molecular basis for enzymatic sulfite oxidation: how three conserved active site residues shape enzyme activity.
J.Biol.Chem., 284:2053-2063, 2009

PubMed Abstract: Sulfite dehydrogenases (SDHs) catalyze the oxidation and detoxification of sulfite to sulfate, a reaction critical to all forms of life. Sulfite-oxidizing enzymes contain three conserved active site amino acids (Arg-55, His-57, and Tyr-236) that are crucial for catalytic competency. Here we have studied the kinetic and structural effects of two novel and one previously reported substitution (R55M, H57A, Y236F) in these residues on SDH catalysis. Both Arg-55 and His-57 were found to have key roles in substrate binding. An R55M substitution increased Km(sulfite)(app) by 2-3 orders of magnitude, whereas His-57 was required for maintaining a high substrate affinity at low pH when the imidazole ring is fully protonated. This effect may be mediated by interactions of His-57 with Arg-55 that stabilize the position of the Arg-55 side chain or, alternatively, may reflect changes in the protonation state of sulfite. Unlike what is seen for SDHWT and SDHY236F, the catalytic turnover rates of SDH R55M and SDHH57A are relatively insensitive to pH (approximately 60 and 200 s(-1), respectively). On the structural level, striking kinetic effects appeared to correlate with disorder (in SDHH57A and SDHY236F) or absence of Arg-55 (SDHR55M), suggesting that Arg-55 and the hydrogen bonding interactions it engages in are crucial for substrate binding and catalysis. The structure of SDHR55M has sulfate bound at the active site, a fact that coincides with a significant increase in the inhibitory effect of sulfate in SDHR55M. Thus, Arg-55 also appears to be involved in enabling discrimination between the substrate and product in SDH.

PubMed: 19004819
DOI: 10.1074/jbc.M807718200

実験手法

X-RAY DIFFRACTION (2 Å)