5XCW

Crystal structure of M92A-M120A double mutant of O-acetyl-L-serine sulfhydrylase from Haemophilus influenzae

5XCW の概要

• エントリーDOI: 10.2210/pdb5xcw/pdb
• 関連するPDBエントリー: 5XCN 5XCP
• 分子名称: Cysteine synthase (2 entities in total)
• 機能のキーワード: pyridoxal phosphate binding, transferase activity, cysteine synthase activity, serine acetyl transferase binding protein, transferase
• 由来する生物種: Haemophilus influenzae (strain ATCC 51907 / DSM 11121 / KW20 / Rd)
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 37084.16

構造登録者

Abhishek, K.,Kumaran, S. (登録日: 2017-03-23, 公開日: 2018-05-02, 最終更新日: 2023-11-22)

主引用文献

Kaushik, A.,Rahisuddin, R.,Saini, N.,Singh, R.P.,Kaur, R.,Kaul, S.,Kumaran, S.
Molecular Mechanism of Selective Substrate Engagement and Inhibitor Dis-engagement of Cysteine Synthase.
J.Biol.Chem., 2020

PubMed Abstract: O-acetyl serine sulfhydrylase (OASS), referred to as cysteine synthase (CS), synthesizes cysteine from O-acetyl serine (OAS) and sulfur in bacteria and plants. The inherent challenge for CS is to overcome 4 to 6 log-folds stronger affinity for its natural inhibitor, serine acetyltransferase (SAT), as compared with its affinity for substrate, OAS. Our recent study showed that CS employs a novel competitive-allosteric mechanism to selectively recruit its substrate in the presence of natural inhibitor. In this study, we trace the molecular features that control selective substrate recruitment. To generalize our findings, we used CS from three different bacteria (Haemophilus, Salmonella, and Mycobacterium) as our model systems and analyzed structural and substrate-binding features of wild-type CS and its ∼13 mutants. Results show that CS uses a noncatalytic residue, M120, located 20 Å away from the reaction center, to discriminate in favor of substrate. M120A and background mutants display significantly reduced substrate binding, catalytic efficiency, and inhibitor binding. Results shows that M120 favors the substrate binding by selectively enhancing the affinity for the substrate and disengaging the inhibitor by 20 to 286 and 5- to 3-folds, respectively. Together, M120 confers a net discriminative force in favor of substrate by 100- to 858-folds.

PubMed: 33162395
DOI: 10.1074/jbc.RA120.014490

実験手法

X-RAY DIFFRACTION (1.89 Å)