Asymmetry of apolipoprotein A-I in solution as assessed from ultracentrifugal, viscometric, and fluorescence polarization studies

Journal Article · Tue Jan 23 04:00:00 EST 1979 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00569a021· OSTI ID:6355463

Barbeau, D L; Jonas, A; Teng, T; Scanu, A M

The solution properties of apoliporprotein A-I (apo A-I) isolated from human and rhesus monkey serum highdensity lipoproteins were examined by the techniques of fluorescence polarization, sedimentaion velocity, sedimentation equilibrium, and viscometry as a function of protein concentration. The ultracentrifugal studies confirmed previous reports that human and rhesus monkey apo A-I undergo a concentration-dependent, reversible self-association in aqueous solutions. The sedimentaion velocity data, extrapolated to infinite dilution, indicated that the apo A-I monomer is asymmetric, with an axial ratio of about 6. The reduced viscosity of apo A-I solutions was also markedly affected by protein concentration; within the range of concentrations studied, the values for human apo A-I ranged from 11.19 to 21.24 mL/g and for rhesus apo A-I, from 8.26 to 16.83 mL/g. The intrinsic viscosity, 6.58 mL/g, of the apo A-I monomer was significantly higher than that of a typical globular protein (3-4 mL/g); the axial ratio, 5.5, was in agreement with that obtained from the ultracentrifugation analyses. In the fluorescence polarization studies, human and rhesus apo A-I were dansylated to the extent of 1.0 to 2.5 mol of dansyl group/mol of apo A-I. This chemical modification was attended by no appreciable change in the secondary structure of apo A-I, as assessed by circular dichroism spectra. The apparent sedimentation coefficient, molecular weight, and rotational relaxation time of each of the dansylated proteins indicated that both human and rhesus monkey apo A-I self-associated to a lesser extent than the unmodified apo A-I. At protein concentrations ranging from 0.002 to 3.0 g/L, the fluorescence polarization values of dansylated apo A-I remained essentially constant (0.185 to 0.192), although rotational relaxation times indicated self-association at the higher concentrations.

• Research Organization: Univ. of Chicago, IL
• OSTI ID: 6355463
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 18:2; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
APOLIPOPROTEINS
ASYMMETRY
BIOCHEMICAL REACTION KINETICS
CENTRIFUGATION
DICHROISM
DISPERSIONS
FLUORESCENCE
KINETICS
LIPIDS
LIPOPROTEINS
LUMINESCENCE
MIXTURES
ORGANIC COMPOUNDS
POLARIZATION
PROTEINS
REACTION KINETICS
SEDIMENTATION
SEPARATION PROCESSES
SOLUTIONS
ULTRACENTRIFUGATION
VISCOSITY