title: Factor D of the alternative pathway of bovine complement: isolation and characterization.
abstract: Factor D of the bovine alternative complement pathway has been purified by chromatography on CM-Sephadex C-50, Sephacryl S-200 and hydroxylapatite. The isolated factor D (0.25 mg from 1 litre of bovine serum) had an apparent molecular weight of 27,500 and a pI of 7.2. In whole bovine serum the pI of factor D was also 7.2. The isolated protein caused the Mg++-dependent cleavage of bovine factor B in the presence of cobra venom factor (CVF) to generate a haemolytically active C3-convertase as shown by SDS-polyacrylamide gel electrophoresis and haemolytic diffusion plate assays. Bovine factor D and human factor D were interchangeable in restoring the alternative pathway haemolytic activities of both bovine RD and human RD (factor D deficient sera). The haemolytic activity of bovine serum factor D was completely inhibited by 20 mM diisopropylfluorophosphate (DFP) but only 25% inhibited by 1 mM DFP. Serum heated at 56 degrees C for 10 min completely lost factor D activity but purified factor D was relatively more heat stable.
mesh_terms: D000818:Animals; D002417:Cattle; D003166:Complement Activating Enzymes / Q000302:isolation & purification*; D003167:Complement Activation; D050577:Complement C3-C5 Convertases / Q000096:biosynthesis; D011416:Complement Factor D / Q000302:isolation & purification* / Q000502:physiology; D003170:Complement Pathway, Alternative; D004546:Elapid Venoms / Q000494:pharmacology; D006801:Humans; D008970:Molecular Weight; D013045:Species Specificity
chemical_list: D004546:Elapid Venoms; C016310:cobra venom factor; D003166:Complement Activating Enzymes; D050577:Complement C3-C5 Convertases; C493488:CFD protein, human; D011416:Complement Factor D