PDBsum entry 1nx7

Electron transport

PDB id: 1nx7

Contents

Protein chain

82 a.a. *

Ligands

HEM

* Residue conservation analysis

References listed in PDB file

Key reference

Title

The comparative study on the solution structures of the oxidized bovine microsomal cytochrome b5 and mutant v45h.

Authors

Q.Zhang, C.Cao, Z.Q.Wang, Y.H.Wang, H.Wu, Z.X.Huang.

Ref.

Protein Sci, 2004, 13, 2161-2169. [DOI no: 10.1110/ps.04721104]

PubMed id

15273310

Abstract

A comparative study on the solution structures of bovine microsomal cytochrome b5 (Tb5) and the mutant V45H has been achieved by 1D and 2D 1H-NMR spectroscopy to clarify the differences in the solution conformations between these two proteins. The results reveal that the global folding of the V45H mutant in solution is unchanged, but the subtle changes exist in the orientation of the axial ligand His39, and heme vinyl groups. The side chain of His45 in V45H mutant extends to the outer edge of the heme pocket leaving a cavity at the site originally occupied by the inner methyl group of Val45 residue. In addition, the imidazole ring of axial ligand His39 rotates counterclockwise by approximately 3 degrees around the His-Fe-His axis, and the 4-heme vinyl group turns to the space vacated by the removed side chain due to the mutation. Furthermore, the helix III of the heme pocket undergoes outward displacement, while the linkage between helix II and III is shifted leftward. These observations are not only consistent with the pattern of the pseudocontact shifts of the heme protons, but also well account for the lower stability of V45H mutant against heat and urea.

Figure 1.
Figure 1. Schematic representation of the short- and medium-range NOE connectivities of proteins: Tb5 (A) and the mutate V45H (B).

Figure 4.
Figure 4. The orientations of the heme moieties and heme vinyl groups in Tb5 and V45H.

The above figures are reprinted by permission from the Protein Society: Protein Sci (2004, 13, 2161-2169) copyright 2004.