One Protein, Two Enzymes Revisited: A Structural Entropy Switch Interconverts the Two Isoforms of Acireductone Dioxygenase

JOURNAL OF MOLECULAR BIOLOGY

卷:363

Article

Ju, Tingting^1,5  Goldsmith, Rachel Beaulieu²  Chai, Sergio C.³  Maroney, Michael J.³  Pochapsky, Susan Sondej¹  Pochapsky, Thomas C.^1,2,4 

[1] Brandeis Univ, Dept Chem, MS 015,415 South St, Waltham, MA 02454 USA

[2] Brandeis Univ, Dept Biochem, MS 015,415 South St, Waltham, MA 02454 USA

[3] Univ Massachusetts, Dept Chem, Amherst, MA 01003 USA

[4] Brandeis Univ, Rosensteil Basic Med Sci Inst, MS 015,415 South St, Waltham, MA 02454 USA

[5] Brown Univ, Dept Mol Pharmacol Physiol & Biotechnol, 70 Ship St, Providence, RI 02912 USA

关键词: metalloenzyme;    paramagnetism;    cupin;   

DOI  :  10.1016/j.jmb.2006.08.060

来源: Elsevier

【 摘 要 】

Acireductone dioxygenase (ARD) catalyzes different reactions between O-2 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. (C) 2006 Elsevier Ltd. All rights reserved.

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