Organic anion transporting polypeptide (OATP) 1B1 is crucial for hepatic uptake of many drugs and endogenous substrates. The clinically relevant OATP1B1 c.521 T>
C (V174A) polymorphism exhibits reduced transport activity in vitro and in vivo in humans. Previously, we reported increased total phosphorylation of V174A-OATP1B1 compared to wild-type (WT)-OATP1B1, although the differentially phosphorylated sites remain to be identified. Lysine-acetylation, a key posttranslational modification (PTM), has not been investigated in OATP1B1. This study aimed to identify differential PTMs of WT-OATP1B1 and V174A-OATP1B1 by quantitatively comparing the relative abundance of modified peptides using liquid chromatography-tandem mass spectrometry-based proteomics and to assess the impact of these PTMs on OATP1B1 transport function using [