Crystal structure of human spermine synthase: Implications of substrate binding and catalytic mechanism

Hong Wu, Jinrong Min, Hong Zeng, Diane E. McCloskey, Yoshihiko Ikeguchi, Peter Loppnau, Anthony J. Michael, Anthony E. Pegg, Alexander N. Plotnikov

Research output: Contribution to journalArticle

67 Citations (Scopus)

Abstract

The crystal structures of two ternary complexes of human spermine synthase (EC 2.5.1.22), one with 5′-methylthioadenosine and spermidine and the other with 5′-methylthioadenosine and spermine, have been solved. They show that the enzyme is a dimer of two identical subunits. Each monomer has three domains: a C-terminal domain, which contains the active site and is similar in structure to spermidine synthase; a central domain made up of four β-strands; and an N-terminal domain with remarkable structural similarity to S-adenosylmethionine decarboxylase, the enzyme that forms the aminopropyl donor substrate. Dimerization occurs mainly through interactions between the N-terminal domains. Deletion of the N-terminal domain led to a complete loss of spermine synthase activity, suggesting that dimerization may be required for activity. The structures provide an outline of the active site and a plausible model for catalysis. The active site is similar to those of spermidine synthases but has a larger substrate-binding pocket able to accommodate longer substrates. Two residues (Asp201 and Asp276) that are conserved in aminopropyltransferases appear to play a key part in the catalytic mechanism, and this role was supported by the results of site-directed mutagenesis. The spermine synthase·5′-methylthioadenosine structure provides a plausible explanation for the potent inhibition of the reaction by this product and the stronger inhibition of spermine synthase compared with spermidine synthase. An analysis to trace possible evolutionary origins of spermine synthase is also described.

Original languageEnglish (US)
Pages (from-to)16135-16146
Number of pages12
JournalJournal of Biological Chemistry
Volume283
Issue number23
DOIs
StatePublished - Jun 6 2008

Fingerprint

Spermine Synthase
Spermidine Synthase
Crystal structure
Spermine
Dimerization
Substrates
Catalytic Domain
Adenosylmethionine Decarboxylase
Mutagenesis
Spermidine
Enzymes
Dimers
Catalysis
Byproducts
Site-Directed Mutagenesis
Monomers

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Wu, H., Min, J., Zeng, H., McCloskey, D. E., Ikeguchi, Y., Loppnau, P., ... Plotnikov, A. N. (2008). Crystal structure of human spermine synthase: Implications of substrate binding and catalytic mechanism. Journal of Biological Chemistry, 283(23), 16135-16146. https://doi.org/10.1074/jbc.M710323200
Wu, Hong ; Min, Jinrong ; Zeng, Hong ; McCloskey, Diane E. ; Ikeguchi, Yoshihiko ; Loppnau, Peter ; Michael, Anthony J. ; Pegg, Anthony E. ; Plotnikov, Alexander N. / Crystal structure of human spermine synthase : Implications of substrate binding and catalytic mechanism. In: Journal of Biological Chemistry. 2008 ; Vol. 283, No. 23. pp. 16135-16146.
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Wu, H, Min, J, Zeng, H, McCloskey, DE, Ikeguchi, Y, Loppnau, P, Michael, AJ, Pegg, AE & Plotnikov, AN 2008, 'Crystal structure of human spermine synthase: Implications of substrate binding and catalytic mechanism', Journal of Biological Chemistry, vol. 283, no. 23, pp. 16135-16146. https://doi.org/10.1074/jbc.M710323200

Crystal structure of human spermine synthase : Implications of substrate binding and catalytic mechanism. / Wu, Hong; Min, Jinrong; Zeng, Hong; McCloskey, Diane E.; Ikeguchi, Yoshihiko; Loppnau, Peter; Michael, Anthony J.; Pegg, Anthony E.; Plotnikov, Alexander N.

In: Journal of Biological Chemistry, Vol. 283, No. 23, 06.06.2008, p. 16135-16146.

Research output: Contribution to journalArticle

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T1 - Crystal structure of human spermine synthase

T2 - Implications of substrate binding and catalytic mechanism

AU - Wu, Hong

AU - Min, Jinrong

AU - Zeng, Hong

AU - McCloskey, Diane E.

AU - Ikeguchi, Yoshihiko

AU - Loppnau, Peter

AU - Michael, Anthony J.

AU - Pegg, Anthony E.

AU - Plotnikov, Alexander N.

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N2 - The crystal structures of two ternary complexes of human spermine synthase (EC 2.5.1.22), one with 5′-methylthioadenosine and spermidine and the other with 5′-methylthioadenosine and spermine, have been solved. They show that the enzyme is a dimer of two identical subunits. Each monomer has three domains: a C-terminal domain, which contains the active site and is similar in structure to spermidine synthase; a central domain made up of four β-strands; and an N-terminal domain with remarkable structural similarity to S-adenosylmethionine decarboxylase, the enzyme that forms the aminopropyl donor substrate. Dimerization occurs mainly through interactions between the N-terminal domains. Deletion of the N-terminal domain led to a complete loss of spermine synthase activity, suggesting that dimerization may be required for activity. The structures provide an outline of the active site and a plausible model for catalysis. The active site is similar to those of spermidine synthases but has a larger substrate-binding pocket able to accommodate longer substrates. Two residues (Asp201 and Asp276) that are conserved in aminopropyltransferases appear to play a key part in the catalytic mechanism, and this role was supported by the results of site-directed mutagenesis. The spermine synthase·5′-methylthioadenosine structure provides a plausible explanation for the potent inhibition of the reaction by this product and the stronger inhibition of spermine synthase compared with spermidine synthase. An analysis to trace possible evolutionary origins of spermine synthase is also described.

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