One site on the apoB-100 specifically binds 17-β-estradiol and regulates the overall structure of LDL

SPECIFIC AIMSBased on our previous report on structural and conformational modifications of apoB-100 in the presence of 17-β-estradiol (E2), we characterized the interaction between this hormone and the apoB-100 and explored the induced alterations in terms of the structural arrangement of the whole LDL particle. We report evidence for the existence on the apoB-100 of a single specific and saturable binding site for E2, whose occupancy modifies the overall structure of the protein, inducing an increase in the α-helix fraction.PRINCIPAL FINDINGS1. E2 binds to a single site in apoB-100 that is saturable, specific, and dependent on the maintenance of a native protein structureData on the binding between E2 and freshly isolated LDL are satisfactorily fitted according to a single class of equivalent binding site model (Fig. 1⤻ A). A linear Scatchard plot (Fig. 1A⤻ , inset) was obtained by plotting the data as a function of bound E2 (ν). The fit yielded one binding site per LDL particle (n=0.8±0.1) with a relat...