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The crystal structure of a sulfurtransferase from Azotobacter vinelandii highlights the evolutionary relationship between the rhodanese and phosphatase enzyme families.

Abstract：

:Rhodanese is an ubiquitous enzyme that in vitro catalyses the transfer of a sulfur atom from suitable donors to nucleophilic acceptors by way of a double displacement mechanism. During the catalytic process the enzyme cycles between a sulfur-free and a persulfide-containing form, via formation of a persulfide linkage to a catalytic Cys residue. In the nitrogen-fixing bacteria Azotobacter vinelandii the rhdA gene has been identified and the encoded protein functionally characterized as a rhodanese. The crystal structure of the A. vinelandii rhodanese has been determined and refined at 1.8 A resolution in the sulfur-free and persulfide-containing forms. Conservation of the overall three-dimensional fold of bovine rhodanese is observed, with substantial modifications of the protein structure in the proximity of the catalytic residue Cys230. Remarkably, the native enzyme is found as the Cys230-persulfide form; in the sulfur-free state the catalytic Cys residue adopts two alternate conformations, reflected by perturbation of the neighboring active-site residues, which is associated with a partly reversible loss of thiosulfate:cyanide sulfurtransferase activity. The catalytic mechanism of A. vinelandii rhodanese relies primarily on the main-chain conformation of the 230 to 235 active-site loop and on a surrounding strong positive electrostatic field. Substrate recognition is based on residues which are entirely different in the prokaryotic and eukaryotic enzymes. The active-site loop of A. vinelandii rhodanese displays striking structural similarity to the active-site loop of the similarly folded catalytic domain of dual specific phosphatase Cdc25, suggesting a common evolutionary origin of the two enzyme families.

journal_name

J Mol Biol

journal_title

Journal of molecular biology

authors

Bordo D,Deriu D,Colnaghi R,Carpen A,Pagani S,Bolognesi M

doi

10.1006/jmbi.2000.3651

keywords:

subject

Has Abstract

pub_date

2000-05-12 00:00:00

pages

691-704

issue

eissn

0022-2836

issn

1089-8638

pii

S0022-2836(00)93651-9

journal_volume

298

pub_type

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The crystal structure of a sulfurtransferase from Azotobacter vinelandii highlights the evolutionary relationship between the rhodanese and phosphatase enzyme families.