Isolation of complement protein D from urine of patients with Fanconi's syndrome

Complement protein D is the least abundant of all complement proteins and, thus, one of the most difficult to purify. We report a new method for obtaining pure D from urine of patients with Fanconi's syndrome. The method is simple and allows the purification of milligram amounts of D within a few days. It involves three chromatographic steps using Bio-Rex 70, hydroxylapatite HPLC, and reverse-phase HPLC. Protein D purified by this method is suitable for both functional and structural studies.