1H7K

Formation of a tyrosyl radical intermediate in Proteus mirabilis catalase by directed mutagenesis and consequences for nucleotide reactivity

Summary for 1H7K

• Entry DOI: 10.2210/pdb1h7k/pdb
• Descriptor: CATALASE, PROTOPORPHYRIN IX CONTAINING FE, ACETATE ION, ... (5 entities in total)
• Functional Keywords: oxidoreductase, oxidoreductase (h2o2 acceptor), peroxidase, iron, hem, hydrogen peroxide, nadp
• Biological source: PROTEUS MIRABILIS
• Total number of polymer chains: 1
• Total formula weight: 56382.75

Authors

Andreoletti, P.,Gambarelli, S.,Gaillard, J.,Sainz, G.,Stojanoff, V.,Jouve, H.M. (deposition date: 2001-07-08, release date: 2004-02-25, Last modification date: 2024-10-23)

Primary citation

Andreoletti, P.,Gambarelli, S.,Sainz, G.,Stojanoff, V.,White, C.,Desfonds, G.,Gagnon, J.,Gaillard, J.,Jouve, H.M.
Formation of a Tyrosyl Radical Intermediate in Proteus Mirabilis Catalase by Directed Mutagenesis and Consequences for Nucleotide Reactivity.
Biochemistry, 40:13734-, 2001

PubMed Abstract: Proteus mirabilis catalase (PMC) belongs to the family of NADPH binding catalases. The function of NADPH in these enzymes is still a matter of debate. This study presents the effects of two independent phenylalanine mutations (F194 and F215), located between NADPH and heme in the PMC structure. The phenylalanines were replaced with tyrosines which we predicted could carry radicals in a NADPH-heme electron transfer. The X-ray crystal structures of the two mutants indicated that neither the binding site of NADPH nor the immediate environment of the residues was affected by the mutations. Measurements using H2O2 as a substrate confirmed that the variants were as active as the native enzyme. With equivalent amounts of peroxoacetic acid, wild-type PMC, F215Y PMC, and beef liver catalase (BLC) formed a stable compound I, while the F194Y PMC variant produced a compound I which was rapidly transformed into compound II and a tyrosyl radical. EPR studies showed that this radical, generated by the oxidation of Y194, was not related to the previously observed radical in BLC, located on Y369. In the presence of excess NADPH, compound I was reduced to a resting enzyme (k(obs) = 1.7 min(-1)) in a two-electron process. This was independent of the enzyme's origin and did not require any thus far identified tyrosyl radicals. Conversely, the presence of a tyrosyl radical in F194Y PMC greatly enhanced the oxidation of reduced beta-nicotinamide mononucleotide under a steady-state H2O2 flow with observable compound II. This process could involve a one-electron reduction of compound I via Y194.

PubMed: 11695923
DOI: 10.1021/BI010687F

Experimental method

X-RAY DIFFRACTION (2.4 Å)