Download MendeleyOne Protein, Two Enzymes Revisited: A Structural Entropy Switch Interconverts the Two Isoforms of Acireductone Dioxygenase
Ju, T., Goldsmith, R.B., Chai, S.C., Maroney, M.J., Pochapsky, S.S., Pochapsky, T.C.(2006) J Mol Biol 363: 823-834
- PubMed: 16989860
- DOI: https://doi.org/10.1016/j.jmb.2006.08.060
- Primary Citation of Related Structures:
2HJI - PubMed 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.
Organizational Affiliation:
Department of Chemistry, Brandeis University, MS 015, Waltham, MA 02454-9110, USA.
