PMID- 19663452
OWN - NLM
STAT- MEDLINE
DCOM- 20090921
LR  - 20211020
IS  - 1520-4995 (Electronic)
IS  - 0006-2960 (Print)
IS  - 0006-2960 (Linking)
VI  - 48
IP  - 34
DP  - 2009 Sep 1
TI  - Sequential dissociation of subunits from bovine heart cytochrome C oxidase by 
      urea.
PG  - 8143-50
LID - 10.1021/bi900773r [doi]
AB  - The quaternary stability of purified, detergent-solubilized, cytochrome c oxidase 
      (CcO) was probed using two chemical denaturants, urea and guanidinium chloride 
      (GdmCl). Each chaotrope induces dissociation of five subunits in a 
      concentration-dependent manner. These five subunits are not scattered over the 
      surface of CcO but are clustered together in close contact at the dimer 
      interface. Increasing the concentration of urea selectively dissociates subunits 
      from CcO in the following order: VIa and VIb, followed by III and VIIa, and 
      finally Vb. After incubation in urea for 10 min at room temperature, the 
      sigmoidal dissociation transitions were centered at 3.7, 4.6, and 7.0 M urea, 
      respectively. The secondary structure of CcO was only minimally perturbed, 
      indicating that urea causes disruption of subunit interactions without 
      urea-induced conformational changes. Incubation of CcO in urea for 120 min 
      produced similar results but shifted the sigmoidal dissociation curves to lower 
      urea concentrations. Incubation of CcO with increasing concentrations of GdmCl 
      produces an analogous effect; however, the GdmCl-induced dissociation of subunits 
      occurs at lower concentrations and with a narrower concentration range. 
      Thermodynamic parameters for each subunit dissociation were evaluated from the 
      sigmoidal dissociation data by assuming a single transition from bound to 
      dissociated subunit. The free energy change accompanying urea-induced 
      dissociation of each subunit ranged from 18.0 to 29.7 kJ/mol, which corresponds 
      to 0.32-0.59 kJ/mol per 100 A(2) of newly exposed solvent-accessible surface 
      area. These values are 30-50-fold smaller than previously reported for the 
      unfolding of soluble or membrane proteins.
FAU - Sedlak, Erik
AU  - Sedlak E
AD  - Department of Biochemistry, The University of Texas Health Science Center, San 
      Antonio, Texas 78229-3900, USA.
FAU - Robinson, Neal C
AU  - Robinson NC
LA  - eng
GR  - R01 GM024795/GM/NIGMS NIH HHS/United States
GR  - R01 GM024795-27/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, N.I.H., Extramural
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Biochemistry
JT  - Biochemistry
JID - 0370623
RN  - 8W8T17847W (Urea)
RN  - EC 1.9.3.1 (Electron Transport Complex IV)
RN  - JU58VJ6Y3B (Guanidine)
SB  - IM
MH  - Animals
MH  - Cattle
MH  - Dose-Response Relationship, Drug
MH  - Electron Transport Complex IV/*chemistry/metabolism
MH  - Guanidine/pharmacology
MH  - Humans
MH  - Myocardium/*enzymology
MH  - Protein Denaturation/drug effects
MH  - Reproducibility of Results
MH  - Thermodynamics
MH  - Urea/*pharmacology
PMC - PMC2745730
MID - NIHMS138096
EDAT- 2009/08/12 09:00
MHDA- 2009/09/22 06:00
PMCR- 2010/09/01
CRDT- 2009/08/12 09:00
PHST- 2009/08/12 09:00 [entrez]
PHST- 2009/08/12 09:00 [pubmed]
PHST- 2009/09/22 06:00 [medline]
PHST- 2010/09/01 00:00 [pmc-release]
AID - 10.1021/bi900773r [doi]
PST - ppublish
SO  - Biochemistry. 2009 Sep 1;48(34):8143-50. doi: 10.1021/bi900773r.