Detergent-solubilized bovine cytochrome c oxidase: dimerization depends on the amphiphilic environment.
The extent to which bovine cytochrome c oxidase (COX) dimerizes in nondenaturing detergent environments was assessed by sedimentation velocity and equilibrium. In contrast to generally accepted opinion, the COX dimer is difficult to maintain and is the major oligomeric form only when COX is solubilized with a low concentration of dodecylmaltoside, i.e., approximately 1 mg/mg protein. The dimer form is intrinsically unstable and dissociates into monomers with increased detergent concentration, i.e., >5 mg/mg protein. The structure of the solubilizing detergent, however, greatly alters detergent effectiveness by inducing either monomerization or aggregation. Triton X-100 is most effective at solubilizing COX, but it destabilizes COX dimers, even at low concentration. Undecylmaltoside, decylmaltoside, and octaethyleneglycolmonododecyl ether (C(12)E(8)) are less effective at solubilizing COX. Each prevents COX aggregation at high detergent concentration, but also destabilizes the COX dimer. Other detergents, e.g., Tween 20, sodium cholate, sodium deoxycholate, CHAPS, or CHAPSO, are completely ineffective COX solubilizers and do not prevent aggregation even at 10-40 mg/mL. The transition from dimers to monomers depends on many factors other than detergent structure and concentration, e.g., protein concentration, phospholipid content and pH. We conclude that the intrinsic dimeric structure of COX can be maintained only after solubilization with low concentrations of dodecylmaltoside at near neutral pH, and even then precautions must be taken to prevent its dissociation into monomers.
Musatov
A
A
Department of Biochemistry, The University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, USA.
Ortega-Lopez
J
J
Robinson
N C
NC
D000818:Animals; D002417:Cattle; D002793:Cholic Acids / Q000737:chemistry; D003840:Deoxycholic Acid / Q000737:chemistry; D003902:Detergents / Q000737:chemistry*; D019281:Dimerization; D003576:Electron Transport Complex IV / Q000737:chemistry*; D005960:Glucosides / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D017830:Octoxynol / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D011136:Polysorbates / Q000737:chemistry; D020358:Sodium Cholate / Q000737:chemistry; D012995:Solubility; D012996:Solutions; D013329:Structure-Activity Relationship
D002793:Cholic Acids; D003902:Detergents; D005960:Glucosides; D011136:Polysorbates; D012996:Solutions; D003840:Deoxycholic Acid; C017272:dodecyloctaethyleneglycol monoether; D011092:Polyethylene Glycols; C040358:dodecyl maltoside; C048531:chapso; D017830:Octoxynol; D003576:Electron Transport Complex IV; D020358:Sodium Cholate; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate