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One protein, two enzymes revisited: a structural entropy switch interconverts the two isoforms of acireductone dioxygenase.
- Source :
-
Journal of molecular biology [J Mol Biol] 2006 Nov 03; Vol. 363 (4), pp. 823-34. Date of Electronic Publication: 2006 Aug 26. - Publication Year :
- 2006
-
Abstract
- Acireductone dioxygenase (ARD) catalyzes different reactions between O2 and 1,2-dihydroxy-3-oxo-5-(methylthio)pent-1-ene (acireductone) depending upon the metal bound in the active site. Ni2+ -ARD cleaves acireductone to formate, CO and methylthiopropionate. If Fe2+ is bound (ARD'), the same substrates yield methylthioketobutyrate and formate. The two forms differ in structure, and are chromatographically separable. Paramagnetism of Fe2+ renders the active site of ARD' inaccessible to standard NMR methods. The structure of ARD' has been determined using Fe2+ binding parameters determined by X-ray absorption spectroscopy and NMR restraints from H98S ARD, a metal-free diamagnetic protein that is isostructural with ARD'. ARD' retains the beta-sandwich fold of ARD, but a structural entropy switch increases order at one end of a two-helix system that bisects the beta-sandwich and decreases order at the other upon interconversion of ARD and ARD', causing loss of the C-terminal helix in ARD' and rearrangements of residues involved in substrate orientation in the active site.
- Subjects :
- Binding Sites
Conserved Sequence
Iron metabolism
Isoenzymes chemistry
Isoenzymes metabolism
Models, Biological
Mutant Proteins chemistry
Peptides chemistry
Protein Structure, Secondary
Stereoisomerism
Structure-Activity Relationship
Dioxygenases chemistry
Dioxygenases metabolism
Entropy
Klebsiella enzymology
Subjects
Details
- Language :
- English
- ISSN :
- 0022-2836
- Volume :
- 363
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Journal of molecular biology
- Publication Type :
- Academic Journal
- Accession number :
- 16989860
- Full Text :
- https://doi.org/10.1016/j.jmb.2006.08.060