Cysteine mutants of human apolipoprotein A-I: a study of secondary structural and functional properties

Zhu, Xuewei; Wu, Gang; Zeng, Weiwei; Xue, Hong; Chen, Baosheng

doi:10.1194/jlr.m400401-jlr200

Cited by 31 publications

(39 citation statements)

References 49 publications

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“…Besides CDO, the cupin superfamily includes several other dioxygenases from all three kingdoms, including pirin that was first characterized structurally by our group (21,22) and was shown to possess quercetin dioxygenase activity by Adams and colleagues (23). Distinct from the other dioxygenases, CDO catalyzes an unusual oxidation reaction in which two oxygen atoms are added to a single atom without C-C bond cleavage in the substrate.…”

mentioning

confidence: 99%

An Insight into the Mechanism of Human Cysteine Dioxygenase

Ye¹,

Wu²,

Wei³

et al. 2007

Journal of Biological Chemistry

165

131

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Cysteine dioxygenase is a non-heme mononuclear iron metalloenzyme that catalyzes the oxidation of cysteine to cysteine sulfinic acid with addition of molecular dioxygen. This irreversible oxidative catabolism of cysteine initiates several important metabolic pathways related to diverse sulfurate compounds. Cysteine dioxygenase is therefore very important for maintaining the proper hepatic concentration of intracellular free cysteine. Mechanisms for mouse and rat cysteine dioxygenases have recently been reported based on their crystal structures in the absence of substrates, although there is still a lack of direct evidence. Here we report the first crystal structure of human cysteine dioxygenase in complex with its substrate L-cysteine to 2.7 Å , together with enzymatic activity and metal content assays of several single point mutants. Our results provide an insight into a new mechanism of cysteine thiol dioxygenation catalyzed by cysteine dioxygenase, which is tightly associated with a thioether-bonded tyrosine-cysteine cofactor involving Tyr-157 and Cys-93. This cross-linked protein-derived cofactor plays several key roles different from those in galactose oxidase. This report provides a new potential target for therapy of diseases related to human cysteine dioxygenase, including neurodegenerative and autoimmune diseases.Cysteine dioxygenase (CDO, 2 EC 1.13.11.20) is a non-heme mononuclear iron metalloenzyme that catalyzes the irreversible oxidation of cysteine to cysteine sulfinic acid (CSA) with addition of molecular oxygen (1) (Structure 1). This oxidative catabolism of cysteine initiates several important metabolic pathways related to pyruvate and several sulfurate compounds, including sulfate, hypotaurine, and taurine. CDO is expressed at appreciable levels in the brain, kidney, and lung, with extremely high levels in liver tissue (2-5), where CDO plays an important role in maintaining the hepatic concentration of intracellular free cysteine within a proper narrow range (6). When the levels of cysteine decrease below this range, the increase of CDO ubiquitination rate results in rapid degradation of the ubiquitinated portion by the 26 S proteasome system (7,8). However, the precise means by which cysteine regulates CDO ubiquitination remain unknown.Intracellular free cysteine is cytotoxic and neuroexcitotoxic due to oxidative damage via formation of free radicals in the presence of iron (9 -11). Elevated cysteine levels were reported previously in relation to several neurodegenerative diseases, including the well known Parkinson and Alzheimer diseases (12-14), and autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis (15, 16). CDO is considered to be involved in these diseases due to its function in regulating free cysteine levels.Sequence alignment classifies CDO as a member of the cupin superfamily (see Fig. 1), whose members possess what may be the most diverse range of functions, encompassing ϳ18 subclasses. Nonetheless, neither of the exact characteristic conserved sequenc...

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mentioning

confidence: 99%

An Insight into the Mechanism of Human Cysteine Dioxygenase

Ye¹,

Wu²,

Wei³

et al. 2007

Journal of Biological Chemistry

165

131

View full text Add to dashboard Cite

show abstract

“…Also, some studies reported enhanced ability of apoA-I M and Milano sera to recruit cell cholesterol ( 32 ), while others reported similar effects of apoA-I M and apoA-I WT in vivo and in vitro (33)(34)(35). Furthermore, enhanced antioxidant activity of apoA-I M was reported in some studies ( 22 ) but not in other studies ( 36 ). In summary, there is no clear consensus regarding the gain-of-function effects of Milano and Paris mutations.…”

Section: Overview Of Function and Structure Of Apoa-i Milano And Apoamentioning

confidence: 88%

“…Second, this rotation is expected to disrupt the aromatic clusters in the N-terminal half of the molecule, which stabilize the four-segment bundle in apoA-I ( 53 ). Such a disruption is indicated strongly by the spectroscopic studies showing largely intact secondary structure but altered aromatic packing and reduced protein stability and unfolding cooperativity of lipid-free apoA-I M as compared with apoA-I WT ( 35,36,47 ). We hypothesize that the rotation of the 1-65 segment away from the 4-segment bundle refl ects a small destabilizing effect of R173C mutation ( 35,36,48 ) in repeat 7 that is an integral part of the bundle ( 53 ).…”

Section: New Insights From the Atomic Structure Of Lipid-free ⌬ (185-mentioning

confidence: 91%

“…Such a disruption is indicated strongly by the spectroscopic studies showing largely intact secondary structure but altered aromatic packing and reduced protein stability and unfolding cooperativity of lipid-free apoA-I M as compared with apoA-I WT ( 35,36,47 ). We hypothesize that the rotation of the 1-65 segment away from the 4-segment bundle refl ects a small destabilizing effect of R173C mutation ( 35,36,48 ) in repeat 7 that is an integral part of the bundle ( 53 ). Such destabilization may result from the disruption of the salt bridge network involving R173 and other charged groups from repeats 7, 2, and 3 in the 4-segment bundle ( 48,53 ), as well as from the structural constraints imposed by the intermolecular disulfi de formed by C173.…”

Section: New Insights From the Atomic Structure Of Lipid-free ⌬ (185-mentioning

confidence: 97%

“…Second, differences in structural stability between apoA-I M and apoA-I WT are also expected to contribute to the enhanced catabolism of apoA-I M . Compared with apoA-I WT , monomeric and disulfi de-linked dimeric apoA-I M in solution was reported to have slightly lower ␣ -helical content ( 36,47,48 ), altered aromatic packing in the N-terminal region ( 47 ), reduced structural stability, and reduced unfolding cooperativity ( 35,49,50 ). Notably, recent hydrogen-deuterium exchange (HX) studies of lipid-free apoA-I by Phillips and colleagues assigned very similar secondary structures to specifi c segments of apoA-I WT and apoA-I M but revealed that the N-terminal half of the apoA-I M molecule adopts two alternative conformations, one similar to that of apoA-I WT and another more accessible to solvent ( 48 ).…”

Section: New Insights From the Atomic Structure Of Lipid-free ⌬ (185-mentioning

confidence: 99%

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