Membrane-surfactant interactions. The role of surfactant in mitochondrial complex III-phospholipid-Triton X-100 mixed micelles

Journal Article · Thu May 15 00:00:00 EDT 1986 · J. Biol. Chem.; (United States)

OSTI ID:5691034

Valpuesta, J M; Arrondo, J L; Barbero, M C; Pons, M; Goni, F M

Complex III (ubiquinol-cytochrome c reductase) was purified from beef heart mitochondria in the form of protein-phospholipid-Triton X-100 mixed micelles (about 1:80:100 molar ratio). Detergent may be totally removed by sucrose density gradient centrifugation, and the resulting lipoprotein complexes retain full enzyme activity. In order to understand the role of surfactant in the mixed micelles, and the interaction of Triton X-100 with integral membrane proteins and phospholipid bilayers, both the protein-lipid-surfactant mixed micelles and the detergent-free lipoprotein system were examined from the point of view of particle size and ultrastructure, enzyme activity, tryptophan fluorescence quenching, 31P NMR, and Fourier transform infrared spectroscopy. The NMR and IR spectroscopic studies show that surfactant withdrawal induces a profound change in phospholipid architecture, from a micellar to a lamellar-like phase. However, electron microscopic observations fail to reveal the existence of lipid bilayers in the absence of detergent. We suggest that, under these conditions, the lipid:protein molar ratio (80:1) is too low to permit the formation of lipid bilayer planes, but the relative orientation and mobility of phospholipids with respect to proteins is similar to that of the lamellar phase. Protein conformational changes are also detected as a consequence of surfactant removal. Fourier transform infrared spectroscopy indicates an increase of peptide beta-structure in the absence of Triton X-100; changes in the amide II/amide I intensity ratio are also detected, although the precise meaning of these observations is unclear.

• Research Organization: Univ. of the Basque Country, Bilbao, Spain
• OSTI ID: 5691034
• Journal Information: J. Biol. Chem.; (United States), Vol. 14
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CELL MEMBRANES
PHYSIOLOGY
OXIDOREDUCTASES
ENZYME ACTIVITY
PURIFICATION
SURFACTANTS
BIOLOGICAL EFFECTS
CENTRIFUGATION
ELECTRON MICROSCOPY
FLUORESCENCE
INFRARED SPECTRA
LIPOPROTEINS
MICELLAR SYSTEMS
MITOCHONDRIA
NUCLEAR MAGNETIC RESONANCE
PARTICLE SIZE
PHOSPHOLIPIDS
PHOSPHORUS 31
POLYETHYLENE GLYCOLS
ALCOHOLS
CELL CONSTITUENTS
ENZYMES
ESTERS
GLYCOLS
HYDROXY COMPOUNDS
ISOTOPES
LIGHT NUCLEI
LIPIDS
LUMINESCENCE
MAGNETIC RESONANCE
MEMBRANES
MICROSCOPY
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANIC POLYMERS
ORGANOIDS
PHOSPHORUS ISOTOPES
POLYMERS
PROTEINS
RESONANCE
SEPARATION PROCESSES
SIZE
SPECTRA
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques