期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 363, 期 4, 页码 823-834出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2006.08.060
关键词
metalloenzyme; paramagnetism; cupin
资金
- U. S. Public Health Service [R01-GM067786]
- National Science Foundation [DBI-9871130]
- NIH Chemistry-Biology Interface Program [T32 GM08515]
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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