Structure and kinetic properties of Paracoccus pantotrophus cytochrome cd(1) nitrite reductase with the d(1) heme active site ligand tyrosine 25 replaced by serine
UNSPECIFIED. (2003) Structure and kinetic properties of Paracoccus pantotrophus cytochrome cd(1) nitrite reductase with the d(1) heme active site ligand tyrosine 25 replaced by serine. JOURNAL OF BIOLOGICAL CHEMISTRY, 278 (14). pp. 11773-11781. ISSN 0021-9258Full text not available from this repository.
Official URL: http://dx.doi.org/10.1074/jbc.M211886200
The 1.4-Angstrom crystal structure of the oxidized state of a Y25S variant of cytochrome cd(1) nitrite reductase from Paracoccus pantotrophus is described. It shows that loss of Tyr(25), a ligand via its hydroxy group to the iron of the d(1) heme in the oxidized (as prepared) wild-type enzyme, does not result in a switch at the e heme of the unusual bishistidinyl coordination to the histidine/methionine coordination seen in other conformations of the enzyme. The Ser(25) side chain is seen in two positions in the d(1) heme pocket with relative occupancies of similar to7:3, but in neither case is the hydroxy group bound to the iron atom; instead, a sulfate ion from the crystallization solution is bound between the Ser(25) side chain and the heme iron. Unlike the wild-type enzyme, the Y25S mutant is active as a reductase toward nitrite, oxygen, and hydroxylamine without a reductive activation step. It is concluded that Tyr(25) is not essential for catalysis of reduction of any substrate, but that the requirement for activation by reduction of the wild-type enzyme is related to a requirement to drive the dissociation of this residue from the active site. The Y25S protein retains the d(1) heme less well than the wild-type protein, suggesting that the tyrosine residue has a role in stabilizing the binding of this cofactor.
|Item Type:||Journal Article|
|Subjects:||Q Science > QD Chemistry|
|Journal or Publication Title:||JOURNAL OF BIOLOGICAL CHEMISTRY|
|Publisher:||AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC|
|Date:||4 April 2003|
|Number of Pages:||9|
|Page Range:||pp. 11773-11781|
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