Structural basis for substrate activation and regulation by cystathionine beta-synthase (CBS) domains in cystathionine β-synthase

Koutmos, Markos; Kabil, Ömer; Smith, Janet L.; Banerjee, Ruma

doi:10.1073/pnas.1011448107

Cited by 100 publications

(263 citation statements)

References 48 publications

(48 reference statements)

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“…1B). We measured CBS activity of purified CG1753 by using radiolabeling methods, and found it to be equally or more active than human CBS, which is in agreement with the high sequence identity (9,10). The heme spectrum of CG1753 protein is also identical to human CBS (Fig.…”

Section: Resultssupporting

confidence: 50%

“…Increased transsulfuration would promote increased cysteine biosynthesis and may allow its use in other pathways (32,33). We find that DR increases dCBS protein more than it does enzyme activity, suggesting that components of the TSP, along with metabolites involved in one-carbon metabolism, might be regulated posttranslationally through modification by sumoylation or allosteric regulation by AdoMet (10,34). Furthermore, the TSP is the primary source of hydrogen sulfide production in the cell (35)(36)(37).…”

Section: Discussionmentioning

confidence: 80%

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Increased transsulfuration mediates longevity and dietary restriction in Drosophila

Kabil

Banerjee

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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The mechanisms through which dietary restriction enhances health and longevity in diverse species are unclear. The transsulfuration pathway (TSP) is a highly conserved mechanism for metabolizing the sulfur-containing amino acids, methionine and cysteine. Here we show that Drosophila cystathionine β-synthase (dCBS), which catalyzes the rate-determining step in the TSP, is a positive regulator of lifespan in Drosophila and that the pathway is required for the effects of diet restriction on animal physiology and lifespan. dCBS activity was up-regulated in flies exposed to reduced nutrient conditions, and ubiquitous or neuron-specific transgenic overexpression of dCBS enhanced longevity in fully fed animals. Inhibition of the TSP abrogated the changes in lifespan, adiposity, and protein content that normally accompany diet restriction. RNAi-mediated knockdown of dCBS also limited lifespan extension by diet. Diet restriction reduced levels of protein translation in Drosophila, and we show that this is largely caused by increased metabolic commitment of methionine cycle intermediates to transsulfuration. However, dietary supplementation of methionine restored normal levels of protein synthesis to restricted animals without affecting lifespan, indicating that global reductions in translation alone are not required for diet-restriction longevity. Our results indicate a mechanism by which dietary restriction influences physiology and aging.hydrogen sulfide | essential amino acids | metabolism | healthspan F or a broad range of taxonomically diverse organisms, the quality of their diet acts as a powerful modulator of health and longevity through molecular mechanisms that are largely unknown. Lifespan is extended, for example, when food is restricted to an extent that falls short of inducing starvation. In mammals, this manipulation, which is often called dietary restriction (DR), not only increases lifespan but also imparts a broad-spectrum improvement in health during aging. In humans, for example, DR reduces risk factors for diabetes, cardiovascular disease, and cancer (1).Transsulfuration is an evolutionarily ancient metabolic process that involves a network of enzymes responsible for the metabolism of sulfur-containing amino acids. The transsulfuration pathway (TSP) has been studied extensively in mammals, in which it has been shown to direct the conversion of homocysteine to cysteine following the breakdown of methionine, an essential amino acid. Flux through the TSP is known to affect overall cellular metabolism by directly influencing cysteine and methionine levels. Methionine availability affects protein synthesis and methylation, and it has been implicated in murine aging (2). Cysteine availability controls the synthesis of glutathione (GSH), which is the chief regulator of cellular redox homeostasis and an important agent in xenobiotic detoxification (Fig. 1A). Patients with genetic defects in the TSP are characterized by high levels of homocysteine, low levels of GSH, and increased incidence of age-related path...

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Section: Resultssupporting

confidence: 50%

Section: Discussionmentioning

confidence: 80%

Increased transsulfuration mediates longevity and dietary restriction in Drosophila

Kabil

Banerjee

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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148

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“…A major contribution of our structure is the unveiling of the relative orientations of the regulatory and catalytic domains in hCBS, which are in striking contrast to the orientation of both the previous in silico models (24,25) and the dCBS structure (21). The hCBS forms a basket-shaped symmetrical dimer in which the catalytic core of each subunit interacts with both the catalytic core and the regulatory domain of the complementary subunit (Fig.…”

Section: Resultsmentioning

confidence: 89%

“…3 C and D). In dCBS, the Bateman module does not interact with the catalytic core except via the connecting linker and associates in a tight dimer through its interfacial α-helices, forming a rare head-to-tailoriented disk-shaped structure referred to as "antiparallel CBS module" (21,26), which differs from the most commonly found head-to-head-oriented assembly (Fig. 3 D and F) (23,27).…”

Section: Resultsmentioning

confidence: 99%

“…The sequence alignment and superimposition of the dCBS structure (21) and an hCBS model defined a loop protruding from the central β-strand of the human CBS2 domain corresponding to the residues 516-525, which we subsequently removed (22). Like the wild-type hCBS, the modified hCBS construct (hCBSOPTΔ516-525) lacking this loop still contains a tandem of CBS motifs (i.e., a Bateman module) in the Cterminal regulatory region (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Structural basis of regulation and oligomerization of human cystathionine β-synthase, the central enzyme of transsulfuration

Ereño‐Orbea

Majtán

Oyenarte

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

157

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Cystathionine β-synthase (CBS) controls the flux of sulfur from methionine to cysteine, a precursor of glutathione, taurine, and H 2 S. CBS condenses serine and homocysteine to cystathionine with the help of three cofactors, heme, pyridoxal-5′-phosphate, and S-adenosyl-L-methionine. Inherited deficiency of CBS activity causes homocystinuria, the most frequent disorder of sulfur metabolism. We present the structure of the human enzyme, discuss the unique arrangement of the CBS domains in the C-terminal region, and propose how they interact with the catalytic core of the complementary subunit to regulate access to the catalytic site. This arrangement clearly contrasts with other proteins containing the CBS domain including the recent Drosophila melanogaster CBS structure. The absence of large conformational changes and the crystal structure of the partially activated pathogenic D444N mutant suggest that the rotation of CBS motifs and relaxation of loops delineating the entrance to the catalytic site represent the most likely molecular mechanism of CBS activation by S-adenosyl-L-methionine. Moreover, our data suggest how tetramers, the native quaternary structure of the mammalian CBS enzymes, are formed. Because of its central role in transsulfuration, redox status, and H 2 S biogenesis, CBS represents a very attractive therapeutic target. The availability of the structure will help us understand the pathogenicity of the numerous missense mutations causing inherited homocystinuria and will allow the rational design of compounds modulating CBS activity.

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Current Structural Knowledge on Cystathionine β‐Synthase, a Pivotal Enzyme in the Transsulfuration Pathway

González‐Recio¹,

Fernández-Rodríguez²,

Simón³

et al. 2020

Encyclopedia of Life Sciences

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Cystathionine β‐synthase (CBS), the first enzyme of the reverse transsulfuration pathway, catalyses the pyridoxal‐5′‐phosphate (PLP)‐dependent β‐replacement reaction that condenses l ‐serine with L‐homocysteine to yield cystathionine and water. Besides this canonical reaction and using cysteine and homocysteine as substrates, CBS can also efficiently produce hydrogen sulfide (H 2 S) through alternative β‐replacement and β‐elimination processes. The structural information on the full‐length enzyme has remained elusive for decades and is still very scarce, but some advances in the recent years have uncovered its peculiar modular architecture, provided a glimpse of its conformational landscape and revealed some of the reaction intermediates formed during the catalysis. All these data have helped comprehend, at least partially, the regulatory mechanisms and the catalytic abilities of the enzyme across different organisms. This article aims to overview the current information on the CBS structure from its most sophisticated variants found in mammals to its simplest homologs in bacteria. A more detailed understanding of CBS structure and function is needed, which could subsequently serve as a basis for the development of drugs to treat human diseases, such as CBS‐deficient homocystinuria, Alzheimer diseases and some cancers, as well as of new antibiotics against multidrug‐resistant pathogenic bacteria. Key Concepts Reverse transsulfuration is a two‐step metabolic route that allows the conversion of the essential amino acid methionine into cysteine. This process generates hydrogen sulfide and impedes the accumulation of the toxic intermediate homocysteine. Hydrogen sulfide is an important gasotransmitter involved in physiological functions such as neuroprotection and the regulation of blood pressure. Homocystinuria consists of the abnormal accumulation of homocysteine, and is an inherited disorder due to the deficient activity of CBS. This pathology causes vascular thromboses, skeletal defects, mental retardation, and even early death. The three‐dimensional structure of CBS provides a suitable template to develop drugs to treat homocystinuria and related pathologies in humans. The comparative structural analysis of the CBS enzymes from different organisms are key to intervene in their sulfur metabolism, and thus represents a potential therapeutic approach against pathogens.

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Structural basis for substrate activation and regulation by cystathionine beta-synthase (CBS) domains in cystathionine β-synthase

Cited by 100 publications

References 48 publications

Increased transsulfuration mediates longevity and dietary restriction in Drosophila

Increased transsulfuration mediates longevity and dietary restriction in Drosophila

Structural basis of regulation and oligomerization of human cystathionine β-synthase, the central enzyme of transsulfuration

Current Structural Knowledge on Cystathionine β‐Synthase, a Pivotal Enzyme in the Transsulfuration Pathway

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