2bh5: Difference between revisions

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.

2BH5 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Paracoccus_versutus Paracoccus versutus] with HEC as [http://en.wikipedia.org/wiki/ligand ligand]. Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2BH5 OCA].  

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