1LJ0

Structure of quintuple mutant of the rat outer mitocondrial cytochrome b5.


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • R-Value Free: 0.251 
  • R-Value Work: 0.207 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Toward engineering the stability and hemin binding properties of microsomal cytochromes b5 into rat outer mitochondrial cytochrome b5: Examining the influence of residues 25 and 71.

Cowley, A.B.Altuve, A.Kuchment, O.Terzyan, S.Zhang, X.C.Rivera, M.Benson, D.

(2002) Biochemistry 41: 11566-11581


  • PubMed Abstract: 
  • As part of a larger effort to engineer the stability and hemin-binding properties of microsomal (Mc) cytochromes b(5) into rat liver outer mitochondrial membrane (OM) cytochrome (cyt) b(5), several mutants of rat OM cyt b(5) were prepared to study th ...

    As part of a larger effort to engineer the stability and hemin-binding properties of microsomal (Mc) cytochromes b(5) into rat liver outer mitochondrial membrane (OM) cytochrome (cyt) b(5), several mutants of rat OM cyt b(5) were prepared to study the effect of gradual and complete elimination of two extended hydrophobic networks, which are present in the structure of the mitochondrial protein and are absent in the structure of mammalian Mc cytochromes b(5). One of the hydrophobic networks, identified in a previous study [Altuve, A., Silchenko, S., Lee, K.-H., Kuczera, K., Terzyan, S., Zhang, X., Benson, D. R., and Rivera, M. (2001) Biochemistry 40, 9469-9483], encompasses the side chains of Ala-18, Ile-32, Leu-36, and Leu-47, whereas a second hydrophobic network, identified as part of this work, encompasses the side chains of Ile-25, Phe-58, Leu-71, and the heme. The X-ray structure of the A18S/I25L/I32L/L47R/L71S quintuple mutant of rat OM cyt b(5) demonstrates that both hydrophobic networks have been eliminated and that the corresponding structural elements of the Mc isoform have been introduced. The stability of the rat OM mutant proteins studied was found to decrease in the order wild type > I25L > A18S/I32L/L47R > L71S > A18S/I32L/L47R/L71S > 18S/I25L/I32L/L47R/L71S, indicating that the two hydrophobic networks do indeed contribute to the high stability of rat OM cyt b(5) relative to the bovine Mc isoform. Surprisingly, the quintuple mutant of rat OM cyt b(5) is less stable than bovine Mc cyt b(5), even though the former exhibits significantly slower rates of hemin release and hemin reorientation at pH 7.0. However, at pH 5.0 the bovine Mc and rat OM quintuple mutant proteins release hemin at comparable rates, suggesting that one or both of the His axial ligands in the rat OM protein are more resistant to protonation under physiological conditions. Results obtained from chemical denaturation experiments conducted with the apoproteins demonstrated that mutants containing L71S are significantly less stable than bovine Mc apocyt b(5), strongly suggesting that Leu-71 plays a pivotal role in the stabilization of rat OM apocyt b(5), presumably via hydrophobic interactions with Ile-25 and Phe-58. Because comparable interactions are absent in bovine Mc apocyt b(5), which contains Ser at position 71, it must resort to different interactions to stabilize its fold, thus highlighting yet another difference between rat OM and bovine Mc cyt b(5). During the course of these investigations we also discovered that rat OM cyt b(5) can be made to strongly favor hemin orientational isomer A (I32L) or isomer B (L71S) with a single point mutation and that release of hemin orientational isomers A and B can be kinetically resolved in certain rat OM mutants.


    Organizational Affiliation

    Department of Chemistry, University of Kansas, Lawrence, KS 66045-7582, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Cytochrome B5 outer mitochondrial membrane isoform
A, B, C, D
92Rattus norvegicusGene Names: Cyb5b (Cyb5m, Omb5)
Find proteins for P04166 (Rattus norvegicus)
Go to UniProtKB:  P04166
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MG
Query on MG

Download SDF File 
Download CCD File 
A, D
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
HEM
Query on HEM

Download SDF File 
Download CCD File 
A, B, C, D
PROTOPORPHYRIN IX CONTAINING FE
HEME
C34 H32 Fe N4 O4
KABFMIBPWCXCRK-RGGAHWMASA-L
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • R-Value Free: 0.251 
  • R-Value Work: 0.207 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 39.753α = 90.00
b = 50.854β = 90.00
c = 167.397γ = 90.00
Software Package:
Software NamePurpose
SCALEPACKdata scaling
CNSrefinement
DENZOdata reduction
CNSphasing

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2002-11-20
    Type: Initial release
  • Version 1.1: 2008-04-28
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance