2bh4
From Proteopedia
X-RAY STRUCTURE OF THE M100K VARIANT OF FERRIC CYT C-550 FROM PARACOCCUS VERSUTUS DETERMINED AT 100 K.
Overview
The structure of cytochrome c-550 from the nonphotosynthetic bacteria Paraccocus versutus has been solved by X-ray crystallography to 1.90 A resolution, and reveals a high structural homology to other bacterial cytochromes c(2). 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 A 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.
About this Structure
2BH4 is a Single protein structure of sequence from Paracoccus versutus. Full crystallographic information is available from OCA.
Reference
The effect of replacing the axial methionine ligand with a lysine residue in cytochrome c-550 from Paracoccus versutus assessed by X-ray crystallography and unfolding., Worrall JA, van Roon AM, Ubbink M, Canters GW, FEBS J. 2005 May;272(10):2441-55. PMID:15885094 Page seeded by OCA on Sat May 3 20:16:47 2008
