PDBsum entry 1cf9

Oxidoreductase

PDB id: 1cf9

Contents

Protein chains

727 a.a. *

Ligands

HEM ×4

Waters ×2686

* Residue conservation analysis

PDB id:

1cf9

Name:

Oxidoreductase

Title:

Structure of the mutant val169cys of catalase hpii from escherichia coli

Structure:

Protein (catalase hpii). Chain: a, b, c, d. Engineered: yes. Mutation: yes

Source:

Escherichia coli. Organism_taxid: 562. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Tetramer (from PQS)

Resolution:

1.80Å R-factor: 0.181 R-free: 0.237

Authors:

M.J.Mate,P.C.Loewen,I.Fita

Key ref:

M.J.Maté et al. (1999). Mutants that alter the covalent structure of catalase hydroperoxidase II from Escherichia coli. J Biol Chem, 274, 27717-27725. PubMed id: 10488114 DOI: 10.1074/jbc.274.39.27717

Date:

24-Mar-99 Release date: 06-Apr-99

Protein chains

P21179  (CATE_ECOLI) -  Catalase HPII from Escherichia coli (strain K12)

Seq: 753 a.a.

Struc: 727 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.1.11.1.6 - catalase.
• Reaction: 2 H2O2 = O2 + 2 H2O
• Cofactor: Heme; Mn(2+)

Heme (Bound ligand (Het Group name = HEM) matches with 95.45% similarity) Mn(2+)

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1074/jbc.274.39.27717

J Biol Chem 274:27717-27725 (1999)

PubMed id: 10488114

Mutants that alter the covalent structure of catalase hydroperoxidase II from Escherichia coli.

M.J.Maté, M.S.Sevinc, B.Hu, J.Bujons, J.Bravo, J.Switala, W.Ens, P.C.Loewen, I.Fita.

ABSTRACT

The three-dimensional structures of two HPII variants, V169C and H392Q, have been determined at resolutions of 1.8 and 2.1 A, respectively. The V169C variant contains a new type of covalent bond between the sulfur atom of Cys(169) and a carbon atom on the imidazole ring of the essential His(128). This variant enzyme has only residual catalytic activity and contains heme b. The chain of water molecules visible in the main channel may reflect the organization of the hydrogen peroxide substrates in the active enzyme. Two alternative mechanisms, involving either compound I or free radical intermediates, are presented to explain the formation of the Cys-His covalent bond. The H392Q and H392E variants exhibit 75 and 25% of native catalytic activity, respectively. The Gln(392) variant contains only heme b, whereas the Glu(392) variant contains a mixture of heme b and cis and trans isomers of heme d, suggesting of a role for this residue in heme conversion. Replacement of either Gln(419) and Ser(414), both of which interact with the heme, affected the cis:trans ratio of spirolactone heme d. Implications for the heme oxidation mechanism and the His-Tyr bond formation in HPII are considered.

Selected figure(s)

Figure 5.
Fig. 5. Reversed-phase HPLC chromatograms for the heme isolated from HPII catalase (A) and the mutant variants H392Q (B), H392E (C), Q419H (D), and S414A (E). The peaks of heme d are indicated by d and the peak of heme b is indicated by b. The faster eluting peak of heme d is the cis isomer and the slower eluting peak is the trans isomer.

Figure 6.
Fig. 6. Possible mechanisms for the formation of the covalent bond found in the V169C variant of HPII between the mutated residue Cys169 and the essential histidine His128. Scheme A shows the proposed nucleophilic mechanism based on the acid catalyzed nucleophilic addition of the thiol group of Cys169 onto the imidazole ring of His128. Scheme B shows an alternate mechanism where protonation of His128, in the initial step of compound I formation, triggers the nucleophilic attack of the thiol group of Cys169 on the imidazole ring. Scheme C depicts the proposed free radical mechanism based on the oxidation of the thiol group of Cys169 to yield a thiyl radical which can attack the imidazolic system.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (1999, 274, 27717-27725) copyright 1999.

Figures were selected by an automated process.