Ultracentrifugal study of the self-association of canine apolipoprotein A-I in solution

Journal Article · Sat Dec 10 04:00:00 EST 1977 · J. Biol. Chem.; (United States)

OSTI ID:7091580

Teng, T L; Edelstein, C; Barbeau, D L; Scanu, A M

The sedimentation behavior of canine apolipoprotein (apo) A-I in 0.02 m EDTA, pH 8.6, was studied as a function of protein concentration by the techniques of sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge. At concentrations of less than 1 g/liter, apo-A-I exhibited a monomodal sedimentation pattern, with apparent sedimentation coefficients which varied from 2.3 to 3.5 S with increasing protein concentrations. Above 1.5 g/liter, apo-A-I had two well resolved peaks with S/sub 20,w/ values of 4.15 S and 5.75 S. The proportion of the 5.75 S component increased with increasing apo-A-I concentrations, with a concomitant decrease of the 4.15 S component. By sedimentation equilibrium ultracentrifugation with both the conventional and meniscus-depletion methods, the apparent weight-average molecular weight of apo-A-I was found to be concentration-dependent. At a protein concentration of 5.25 g/liter, an apparent weight average molecular weight of 138,000 was determined, indicating that molecular species larger than a tetramer (monomer molecular weight = 28,000) were present in solution. When analyzed in terms of a reversible self-associating system, the experimental data could best be described according to a monomer-dimer-tetramer-octamer model, as previously reported for human apo-A-I (Vitello, L. B., and Scanu, A. M. (1975) J. Biol. Chem. 251, 1131-1136). The equilibrium constants were: K/sub 2/ = 4.5 liters/g, K/sub 4/ = 470 liters/sup 3//g/sup 3/, and K/sub 8/ = 41,600 liters/sup 7//g/sup 7/, respectively.

• Research Organization: Univ. of Chicago
• OSTI ID: 7091580
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 252:23; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ABSORPTION
ANIMALS
AQUEOUS SOLUTIONS
BEAGLES
BLOOD SERUM
CENTRIFUGATION
DISPERSIONS
DOGS
LIPIDS
LIPOPROTEINS
MAMMALS
MIXTURES
MOLECULAR WEIGHT
ORGANIC COMPOUNDS
PROTEINS
SEDIMENTATION
SELF-ABSORPTION
SEPARATION PROCESSES
SOLUBILITY
SOLUTIONS
ULTRACENTRIFUGATION
VERTEBRATES