Distribution and characterization of apolipoproteins in Chrysemys picta plasma

Very low density lipoproteins (VLDL) (d < 1.006), low density lipoproteins (LDL) (1.006 < d < 1.063), and high density lipoproteins (HDL) (1.063 < d < 1.21) were isolated by ultracentrifugation from the plasma of female and male Chrysemys picta. The protein components of lipoproteins (apolipoproteins) were analysed by electrophoresis in denaturing polyacrylamide gradient gel. Gel filtration chromatography, electroelution from gradient gel and two dimensional electrophoresis were utilized to partially purify and characterized the main apolipoproteins. A 350 kDa Apo B-like protein was found associated with VLDL and LDL fractions. In HDL, Apo AI was the main protein component which, after purification on Sephadex G-200, showed the same electrophoretic mobility as human Apo AI (28 kDa). When analysed by two dimensional electrophoresis, Apo AI gave a pI value of 5.2. A 36 kDa apolipoprotein was purified from VLDL fraction. The purified putative Apo E showed an electrophoretic mobility slightly lower than human Apo E (34 kDa). The only sex difference observed was a band in the female bottom fraction (d > 1.21) with similar electrophoretic mobility to vitellogenin.