COL4A3BP is a member of the StarD2 subfamily. It contains a pleckstrin homology domain at its amino terminus and a START domain towards the end of the molecule. COL4A3BP has a lipid-binding domain that mediates intracellular trafficking of ceramide in a non-vesicular manner. One isoform of COL4A3BP is also involved in ceramide intracellular transport. COL4A3BP specifically phosphorylates the N-terminal region of the non-collagenous domain of the alpha 3 chain of type IV collagen, known as the Goodpasture antigen. An autoimmune response directed at this antigen can cause goodpasture disease.