Figure 5. PON1 Tyr₇₁ is a functionally important site for HDL interaction and a target for MPO-catalyzed oxidation in human atherosclerotic plaque.

(A) Schematic illustration of photocholestanyl-labeled PON1 tyrosyl residue. (B) Reconstituted HDL formed using POPC/photocholesterol/APOA1 (100:10:1) was incubated with PON1 and exposed to UV light as described in Methods. Proteomics studies revealed the photocholestanyl adduct of PON1 Tyr₇₁ [Y(ch)] as a site on PON1 that directly interacts with cholesterol as described in Methods. m/z, mass-to-charge ratio. (C) PON1 crystal structure with superimposed location of Tyr₇₁ (red) and hypothetical HDL binding surface based on hydrophobicity analysis. (D) Recombinant human WT PON1 versus the indicated PON1 Tyr₇₁ site–specific mutants were generated, isolated, incubated with HDL, and then paraoxonase activity was determined as described in Methods. Results represent the mean ± SD from at least 3 independent experiments.