Calcium-dependent binding of uteroglobin (PCB-BP/CCSP) to negatively charged phospholipid liposomes

To investigate interactions between the polychlorinated biphenyl-binding protein uteroglobin and phospholipids, we used a liposome-pelletting assay. PCB-BP/uteroglobin bound to liposomes made from negatively charged phospholipids (PtdSer and PtdIns) in the presence of 5 mM calcium. No binding to liposomes made from phospholipids without net charge (PtdChol and PtdEtn) was observed, nor could we detect binding in the absence of calcium or when magnesium was substituted for calcium. This suggests that PCB-BP/uteroglobin can bind to phospholipids in vivo and may have a role in the phospholipid homeostasis of the airway and/or secretory pathway of the Clara cell.