1pl3
From Proteopedia
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Cytochrome Domain Of Cellobiose Dehydrogenase, M65H mutant
Overview
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.
About this Structure
1PL3 is a Single protein structure of sequence from Phanerochaete chrysosporium with CD, HEM and 1PG as ligands. Active as Cellobiose dehydrogenase (acceptor), with EC number 1.1.99.18 Full crystallographic information is available from OCA.
Reference
Biophysical and structural analysis of a novel heme B iron ligation in the flavocytochrome cellobiose dehydrogenase., Rotsaert FA, Hallberg BM, de Vries S, Moenne-Loccoz P, Divne C, Renganathan V, Gold MH, J Biol Chem. 2003 Aug 29;278(35):33224-31. Epub 2003 Jun 9. PMID:12796496
Page seeded by OCA on Tue Nov 20 23:54:13 2007
