The crystal structure of human S-adenosylmethionine decarboxylase at 2.25 Å resolution reveals a novel fold

Ekstrom, J.L.; Mathews, I.I.; Stanley, Bruce A.; Pegg, Anthony E.; Ealick, S.E.

doi:10.1016/s0969-2126(99)80074-4

Cited by 72 publications

(126 citation statements)

References 39 publications

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“…Such cumulative evidence strongly suggests that inactivation of AdoMetDC can be attributed not just to change in the conformation of the enzyme, but to modification of the active site amino acid residue. Our results from Arabidopsis thaliana AdoMetDC are in agreement with that of human AdoMetDC (Ekstrom et al, 1999). Because of the instability of C50A and C230A AdoMetDC mutants that were encountered during experimental manipulation, the possibility that the mutations may have altered thermal stability was examined.…”

Section: Discussionsupporting

confidence: 82%

“…However, there are no reports on the structurally important amino acid residues of the Arabidopsis thaliana AdoMetDC. Therefore, possible candidate residues for mutagenesis were selected from the human AdoMetDC crystal structure (Ekstrom et al, 1999) and previous study (Park and Cho, 1999). Mutagenesis of the AdoMetDC coding sequence was performed by sequential PCR.…”

Section: Resultsmentioning

confidence: 99%

“…Arabidopsis thaliana AdoMetDC was predicted to have 6 α-helices with length 4-22 residues and 16 b-sheets with length 2-12 residues for the monomer. Human AdoMetDC has 9 α-helices of 4-18 residues and 15 β-sheets of 2-8 residues (Ekstrom et al, 1999). The PRIpred-predicted secondary structure of Arabidopsis thaliana AdoMetDC is generally similar to that of human AdoMetDC with a few different structures due to the sequence variation (Fig.…”

Section: Circular Dichroism Analysismentioning

confidence: 88%

“…On the contrary, site-directed mutagenesis of alaninelysine residues of inorganic pyrophosphatase decreased the thermal stability (Satoh et al, 1999). According to human AdoMetDC crystallographic studies, the Cys 49 and Cys 226 residues, counterparts of Cys 50 and Cys 230 in Arabidopsis thaliana, were not a component of α-helix within AdoMetDC, but are rather at the beginning of the β-sheet, strand β2, and strand β11, respectively (Ekstrom et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

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Structural Roles of Cysteine 50 and Cysteine 230 Residues in Arabidopsis thaliana S-Adenosylmethionine Decarboxylase

Park¹,

Cho²

2002

BMB Reports

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TheArabidopsis thaliana S-Adenosylmethionine decarboxylase (AdoMetDC) cDNA (GenBank TM U63633) was cloned. Site-specific mutagenesis was performed to introduce mutations at the conserved cysteine Cys 50 , Cys 83 , and Cys 230 , and lys 81 residues. In accordance with the human AdoMetDC, the C50A and C230A mutagenesis had minimal effect on catalytic activity, which was further supported by DTNB-mediated inactivation and reactivation. However, unlike the human AdoMetDC, the Cys 50 and Cys 230 mutants were much more thermally unstable than the wild type and other mutant AdoMetDC, suggesting the structural significance of cysteines. Furthermore, according to a circular dichroism spectrum analysis, the Cys 50 and Cys 230 mutants show a higher a-helix content and lower coiled-coil content when compared to that of wild type and the other mutant AdoMetDC. Also, the three-dimensional structure of Arabidopsis thaliana AdoMetDC could further support all of the data presented here. Summarily, we suggest that the Cys 50 and Cys 230 residues are structurally important.

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Section: Discussionsupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Circular Dichroism Analysismentioning

confidence: 88%

Section: Discussionmentioning

confidence: 99%

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Structural Roles of Cysteine 50 and Cysteine 230 Residues in Arabidopsis thaliana S-Adenosylmethionine Decarboxylase

Park¹,

Cho²

2002

BMB Reports

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“…Alternately, in mammalian cells alanine has been shown to be a destabilizing residue in the N-end rule demonstrated by Varshavsky and co-workers (53), so pyruvoyl transamination to alanine could create a destabilizing N-terminal amino acid. However, the pyruvoyl residue, as well as the cysteine active site residue, which may be alkylated as part of the transamination process (36), are located in an internal cleft of the enzyme (41), and thus unlikely to serve as surface-accessible signals or sites for ubiquitination. It seems more likely that transamination/alkylation accelerates the overall degradation rate by altering the structure of the enzyme in such a way as to expose an internal targeting signal or ubiquitination site, which is then recognized by the ubiquitin conjugation machinery.…”

Section: Fig 4 Effect Of Inhibition Of the 26 S Proteasome Onmentioning

confidence: 99%

S-Adenosylmethionine Decarboxylase Degradation by the 26 S Proteasome Is Accelerated by Substrate-mediated Transamination

Yerlikaya

Stanley

2004

Journal of Biological Chemistry

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The short-lived enzyme S-adenosylmethionine decarboxylase uses a covalently bound pyruvoyl cofactor to catalyze the formation of decarboxylated S-adenosylmethionine, which then donates an aminopropyl group for polyamine biosynthesis. Here we demonstrate that S-adenosylmethionine decarboxylase is ubiquitinated and degraded by the 26 S proteasome in vivo, a process that is accelerated by inactivation of S-adenosylmethionine decarboxylase by substrate-mediated transamination of its pyruvoyl cofactor. Proteasome inhibition in COS-7 cells prevents the degradation of S-adenosylmethionine decarboxylase antigen; however, even brief inhibition of the 26 S proteasome caused substantial losses of S-adenosylmethionine decarboxylase activity despite accumulation of S-adenosylmethionine decarboxylase antigen. Levels of the enzyme's substrate (S-adenosylmethionine) increased rapidly after 26 S proteasome inhibition, and this increase in substrate level is consistent with the observed loss of activity arising from an increased rate of inactivation by substrate-mediated transamination. Evidence is also presented that this substrate-mediated transamination accelerates normal degradation of S-adenosylmethionine decarboxylase, as the rate of degradation of the enzyme was increased in the presence of AbeAdo (5 -([(Z)-4-amino-2-butenyl]methylamino]-5 -deoxyadenosine) (a substrate analogue that transaminates the enzyme); conversely, when the intracellular substrate level was reduced by methionine deprivation, the rate of degradation of the enzyme was decreased. Ubiquitination of S-adenosylmethionine decarboxylase is demonstrated by isolation of His-tagged AdoMetDC (S-adenosylmethionine decarboxylase) from COS-7 cells co-transfected with hemagglutinin-tagged ubiquitin and showing bands that were immunoreactive to both anti-AdoMetDC antibody and anti-hemagglutinin antibody. This is the first study to demonstrate that AdoMetDC is ubiquitinated and degraded by the 26 S proteasome, and substrate-mediated acceleration of degradation is a unique finding.

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Comparative properties of a three‐dimensional model of Plasmodium falciparum ornithine decarboxylase

et al. 2003

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The ornithine decarboxylase (ODC) component of the bifunctional S-adenosylmethionine decarboxylase/ornithine decarboxylase enzyme (PfAdoMetDC-ODC) of Plasmodium falciparum was modeled on the crystal structure of the Trypanosoma brucei enzyme. The homology model predicts a doughnut-shaped active homodimer that associates in a head-to-tail manner. The monomers contain two distinct domains, an N-terminal alpha/beta-barrel and a C-terminal modified Greek-key domain. These domains are structurally conserved between eukaryotic ODC enzymes and are preserved in distant analogs such as alanine racemase and triosephosphate isomerase-like proteins. Superimposition of the PfODC model on the crystal structure of the human enzyme indicates a significant degree of deviation in the carbon alpha-backbone of the solvent accessible loops. The surface locality of the ab initio modeled 38 amino acid parasite-specific insert suggests a role in the stabilization of the large bifunctional protein complex. The active site pockets of PfODC at the interface between the monomers appear to be conserved regarding the binding sites of the cofactor and substrate, but each contains five additional malaria-specific residues. The predicted PfODC homology model is consistent with mutagenesis results and biochemical studies concerning the active site residues and areas involved in stabilizing the dimeric form of the protein. Two competitive inhibitors of PfODC could be shown to interact with several parasite-specific residues in comparison with their interaction with the human ODC. The PfODC homology model contributes toward a structure-based approach for the design of novel malaria-specific inhibitors.

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The crystal structure of human S-adenosylmethionine decarboxylase at 2.25 Å resolution reveals a novel fold

Cited by 72 publications

References 39 publications

Structural Roles of Cysteine 50 and Cysteine 230 Residues in Arabidopsis thaliana S-Adenosylmethionine Decarboxylase

Structural Roles of Cysteine 50 and Cysteine 230 Residues in Arabidopsis thaliana S-Adenosylmethionine Decarboxylase

S-Adenosylmethionine Decarboxylase Degradation by the 26 S Proteasome Is Accelerated by Substrate-mediated Transamination

Comparative properties of a three‐dimensional model of Plasmodium falciparum ornithine decarboxylase

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