Back to Search
Start Over
Crystal Structure of the Heme d1 Biosynthesis Enzyme NirE in Complex with Its Substrate Reveals New Insights into the Catalytic Mechanism of S-Adenosyl-L-methionine-dependent Uroporphyrinogen III Methyltransferases.
- Source :
-
Journal of Biological Chemistry . 7/29/2011, Vol. 286 Issue 30, p26754-26767. 14p. - Publication Year :
- 2011
-
Abstract
- During the biosynthesis of heme d1, the essential cofactor of cytochrome cd1 nitrite reductase, the NirE protein catalyzes the methylation of uroporphyrinogen III to precorrin-2 using S-adenosyl-l-methionine (SAM) as the methyl group donor. The crystal structure of Pseudomonas aeruginosa NirE in complex with its substrate uroporphyrinogen III and the reaction by-product S-adenosyl-l-homocysteine (SAH) was solved to 2.0 Å resolution. This represents the first enzyme-substrate complex structure for a SAM-dependent uroporphyrinogen III methyltransferase. The large substrate binds on top of the SAH in a "puckered" conformation in which the two pyrrole rings facing each other point into the same direction either upward or downward. Three arginine residues, a histidine, and a methionine are involved in the coordination of uroporphyrinogen III. Through site-directed mutagenesis of the nirE gene and biochemical characterization of the corresponding NirE variants the amino acid residues Arg-111, Glu-114, and Arg-149 were identified to be involved in NirE catalysis. Based on our structural and biochemical findings, we propose a potential catalytic mechanism for NirE in which the methyl transfer reaction is initiated by an arginine catalyzed proton abstraction from the C-20 position of the substrate. [ABSTRACT FROM AUTHOR]
- Subjects :
- *BIOSYNTHESIS
*CYTOCHROMES
*PSEUDOMONAS aeruginosa
*METHIONINE
*ARGININE
*AMINO acids
Subjects
Details
- Language :
- English
- ISSN :
- 00219258
- Volume :
- 286
- Issue :
- 30
- Database :
- Academic Search Index
- Journal :
- Journal of Biological Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 64294561
- Full Text :
- https://doi.org/10.1074/jbc.M111.239855