1PL3

Cytochrome Domain Of Cellobiose Dehydrogenase, M65H mutant

Summary for 1PL3

• Entry DOI: 10.2210/pdb1pl3/pdb
• Related: 1D7B 1D7C 1D7D 1KDG 1NAA
• Descriptor: Cellobiose dehydrogenase, 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, CADMIUM ION, ... (6 entities in total)
• Functional Keywords: b-type cytochrome, mutant, bis-his ligation, beta sandwich, fe(ii)-protoporphyrin ix, oxidoreductase
• Biological source: Phanerochaete chrysosporium
• Total number of polymer chains: 2
• Total formula weight: 43047.99

Authors

Rotsaert, F.A.J.,Hallberg, B.M.,de Vries, S.,Moenne-Loccoz, P.,Divne, C.,Gold, M.H. (deposition date: 2003-06-06, release date: 2003-07-01, Last modification date: 2024-11-13)

Primary citation

Rotsaert, F.A.J.,Hallberg, B.M.,De Vries, S.,Moenne-Loccoz, P.,Divne, C.,Renganathan, V.,Gold, M.H.
Biophysical and Structural Analysis of a Novel Heme b Iron Ligation in the Flavocytochrome Cellobiose Dehydrogenase.
J.Biol.Chem., 278:33224-33231, 2003

PubMed Abstract: The fungal extracellular flavocytochrome cellobiose dehydrogenase (CDH) participates in lignocellulose degradation. The enzyme has a cytochrome domain connected to a flavin-binding domain by a peptide linker. The cytochrome domain contains a 6-coordinate low spin b-type heme with unusual iron ligands and coordination geometry. Wild type CDH is only the second example of a b-type heme with Met-His ligation, and it is the first example of a Met-His ligation of heme b where the ligands are arranged in a nearly perpendicular orientation. To investigate the ligation further, Met65 was replaced with a histidine to create a bis-histidyl ligated iron typical of b-type cytochromes. The variant is expressed as a stable 90-kDa protein that retains the flavin domain catalytic reactivity. However, the ability of the mutant to reduce external one-electron acceptors such as cytochrome c is impaired. Electrochemical measurements demonstrate a decrease in the redox midpoint potential of the heme by 210 mV. In contrast to the wild type enzyme, the ferric state of the protoheme displays a mixed low spin/high spin state at room temperature and low spin character at 90 K, as determined by resonance Raman spectroscopy. The wild type cytochrome does not bind CO, but the ferrous state of the variant forms a CO complex, although the association rate is very low. The crystal structure of the M65H cytochrome domain has been determined at 1.9 A resolution. The variant structure confirms a bis-histidyl ligation but reveals unusual features. As for the wild type enzyme, the ligands have a nearly perpendicular arrangement. Furthermore, the iron is bound by imidazole N delta 1 and N epsilon 2 nitrogen atoms, rather than the typical N epsilon 2/N epsilon 2 coordination encountered in bis-histidyl ligated heme proteins. To our knowledge, this is the first example of a bis-histidyl N delta 1/N epsilon 2-coordinated protoporphyrin IX iron.

PubMed: 12796496
DOI: 10.1074/jbc.M302653200

Experimental method

X-RAY DIFFRACTION (1.9 Å)