In crystallo posttranslational modification within a MauG/pre-methylamine dehydrogenase complex - PubMed (original) (raw)

In crystallo posttranslational modification within a MauG/pre-methylamine dehydrogenase complex

Lyndal M R Jensen et al. Science. 2010.

Abstract

MauG is a diheme enzyme responsible for the posttranslational modification of two tryptophan residues to form the tryptophan tryptophylquinone (TTQ) cofactor of methylamine dehydrogenase (MADH). MauG converts preMADH, containing monohydroxylated betaTrp57, to fully functional MADH by catalyzing the insertion of a second oxygen atom into the indole ring and covalently linking betaTrp57 to betaTrp108. We have solved the x-ray crystal structure of MauG complexed with preMADH to 2.1 angstroms. The c-type heme irons and the nascent TTQ site are separated by long distances over which electron transfer must occur to achieve catalysis. In addition, one of the hemes has an atypical His-Tyr axial ligation. The crystalline protein complex is catalytically competent; upon addition of hydrogen peroxide, MauG-dependent TTQ synthesis occurs.

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Figures

Figure 1

Figure 1

(A) Overall ribbon representation of the MauG-preMADH complex. (B) Spatial layout of potential redox groups. Color scheme is MauG (pink); preMADH α (blue) and β (green). The hemes, Trp93, Trp199 of MauG and βTrp108 and mono-hydroxylated βTrp57 of preMADH are drawn explicitly in a stick representation. Figure produced using PyMOL (

http://www.pymol.org/

).

Figure 2

Figure 2

Site of TTQ formation in MADH. (A) 2Fo-Fc electron density for the MauG-preMADH complex (resolution 2.1 Å). (B) The first 2Fo-Fc electron density calculated with MauG-preMADH + H2O2 structure factors (resolution 2.1 Å) and MauG-preMADH model phases with the preMADH βTrp57 and βTrp108 side-chains omitted. Electron densities were contoured at 1 σ. Carbon coloring: preMADH, light green; preMADH + H2O2, dark green. Figure produced using PyMOL (

http://www.pymol.org/

).

Figure 3

Figure 3

MauG hemes. (A) 6-coordinate low-spin heme (CHE600), (B) 5-coordinate high-spin heme (CHE500), and (C) residues that line the distal pocket. 2Fo-Fc electron density contoured at 1 σ. Figure produced using PyMOL (

http://www.pymol.org/

).

Scheme 1

Scheme 1

Overall reaction catalyzed by MauG

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