Two retinol binding proteins in Lewis lung tumor cytosol

Cellular retinol binding protein is present in the cytosol of Lewis lung primary tumor, as detected by DEAE-filter disk method. Gel filtration, followed by non-denaturing polyacrylamide gel electrophoresis, reveals the presence of two binding components. One of them binds retinol specifically as the [3H]retinol can be replaced by unlabeled retinol, but not by unlabeled retinoic acid. In contrast, [3H]retinol radioactivity of the second binding component can be abolished by both unlabeled retinol and unlabeled retinoic acid. SDS polyacrylamide gel electrophoresis shows that the two components have similar migration distances which correspond to an apparent molecular weight of 15,000.