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- Title
The effect of replacing the axial methionine ligand with a lysine residue in cytochrome c-550 fromParacoccus versutusassessed by X-ray crystallography and unfolding.
- Authors
Worrall, Jonathan A. R.; van Roon, Anne-Marie M.; Ubbink, Marcellus; Canters, Gerard W.
- Abstract
The structure of cytochromec-550 from the nonphotosynthetic bacteriaParaccocus versutushas been solved by X-ray crystallography to 1.90 Å resolution, and reveals a high structural homology to other bacterial cytochromesc2. The effect of replacing the axial heme-iron methionine ligand with a lysine residue on protein structure and unfolding has been assessed using the M100K variant. From X-ray structures at 1.95 and 1.55 Å resolution it became clear that the amino group of the lysine side chain coordinates to the heme-iron. Structural differences compared to the wild-type protein are confined to the lysine ligand loop connecting helices four and five. In the heme cavity an additional water molecule is found which participates in an H-bonding interaction with the lysine ligand. Under cryo-conditions extra electron density in the lysine ligand loop is revealed, leading to residues K97 to T101 being modeled with a double main-chain conformation. Upon unfolding, dissociation of the lysine ligand from the heme-iron is shown to be pH dependent, with NMR data consistent with the occurrence of a ligand exchange mechanism similar to that seen for the wild-type protein.
- Subjects
METHIONINE; LYSINE; CYTOCHROME c; X-rays; CRYSTALLOGRAPHY; HYDROGEN bonding
- Publication
FEBS Journal, 2005, Vol 272, Issue 10, p2441
- ISSN
1742-464X
- Publication type
Article
- DOI
10.1111/j.1742-4658.2005.04664.x