Therefore, by the term gp330 is meant the glycoprotein from the renal tubule fraction of normalrat kidneys from the SpragueDawley or the Lewis strain having a band on SDS-PAGE corresponding to M.sub.r =440 kD. The homologous molecule from other strains of rats may have similar but variant molecular weights, as is well known in the art.A functional derivative of gp330 is a compound which posses