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Structural bases for inhibitor binding and catalysis in polyamine oxidase
C Binda1, R Angelini, R Federico
1Dipartimento di Genetica e Microbiologia, Università di Pavia, Via Abbiategrasso 207, I-27100 Pavia, Italy.
Biochemistry
|March 22, 2001
Summary
Polyamine oxidase (PAO) structure reveals a lock-and-key binding mechanism for inhibitors. This insight into PAO substrate specificity and amine oxidation may aid in designing targeted drugs.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Polyamine oxidase (PAO) catalyzes FAD-dependent oxidation of polyamines, crucial for catabolism.
- PAO features a 30 Å U-shaped catalytic tunnel leading to the flavin ring.
Purpose of the Study:
- Investigate maize PAO substrate specificity and amine oxidation mechanism.
- Determine the crystal structure of PAO in reduced state and complex with inhibitors.
Main Methods:
- X-ray crystallography of maize PAO.
- Structural analysis of PAO in reduced state and complex with guazatine, 1,8-diaminooctane, and CHENSpm.
Main Results:
- PAO structure is similar in oxidized and reduced states, with minor Lys300 movement.
- Inhibitors exhibit precise lock-and-key binding within the PAO catalytic tunnel without protein conformational changes.
- CHENSpm forms a covalent adduct with the flavin N5 atom.
- An "out-of-register" inhibition mechanism is suggested, where inhibitor alignment prevents oxidation.
Conclusions:
- PAO recognition of substrates/inhibitors primarily involves non-charged residues, unlike other polyamine-binding proteins.
- The identified binding mode and unique recognition features offer potential for PAO-specific drug design.