Purification of proteins with cationic surfactant

Abstract

The subject invention provides a method for purifying a target protein from a mixture comprising the target protein and contaminating protein, comprising the steps of exposing the mixture to an effective amount of a cationic surfactant such that the contaminating protein is preferentially precipitated and recovering the target protein. Proteins purified according to the method of the invention are also provided.

1 - 48 . (canceled) 
     
     
         49 . A method for purifying a uricase comprising:
 (a) obtaining a solution comprising a mixture of a solubilized uricase, one or more solubilized contaminating proteins and an alkaline buffer, wherein the uricase is positively charged under alkaline pH and has an isoelectric point greater than or equal to 7 and the one or more contaminating proteins has a polyanion charge;   (b) contacting the solution comprising the mixture of the solubilized uricase and the one or more solubilized contaminating proteins with one or more cationic surfactants in an amount effective to preferentially precipitate the one or more contaminating proteins, thereby increasing the proportion of proteins remaining in solution represented by the uricase; and   (c) recovering the uricase in solution after the preferential precipitation of step (b);   wherein the uricase comprises at least 90% of the total protein in the solution;   wherein the method is performed in the absence of a solid support and wherein at least one of the one or more cationic surfactants is an amphipathic ammonium compound selected from the group consisting of a quaternary ammonium compound of the general formula QN+; a paraffin chain primary ammonium compound of the general formula RNH3+; and a salt thereof.   
     
     
         50 . The method of  claim 49 , wherein the amphipathic ammonium compound is selected from the group consisting of cetylpyridinium salts, stearamide-methylpyridinium salts, lauryl pyridinium salts, cetylquinolynium salts, lauryl aminopropionic acid methyl ester salts, lauryl amino propionic acid metal salts, lauryl dimethyl betaine, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine and benzethonium salts. 
     
     
         51 . The method of  claim 50 , wherein the amphipathic ammonium compound is selected from hexadecylpyridinium chloride, dequalinium acetate, hexadecylpyridinium chloride, cetyltrimethylammonium chloride, mixed N-alkyl dimethyl benzylammonium chloride, cetylpyridinium chloride, N,N-dimethyl-N-[2-[2-[4-(1,1,3,3,-tetramethylbutyl)-phenoxy]ethoxy]ethyl] benzenemethanammonium chloride, alkyl-dimethylbenzyl-ammonium chloride, and dichloro-benzyldimethyl-alkylammonium chloride, tetradecyl trimethylammonium bromide, dodecyl trimethylammonium bromide, cetyltrimethylammonium bromide, lauryl dimethyl betaine stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine. 
     
     
         52 . The method of  claim 50 , wherein the amphipathic ammonium compound is a cetylpyridinium salt. 
     
     
         53 . The method of  claim 52 , wherein the cetylpyridinium salt is cetylpyridinium chloride. 
     
     
         54 . The method of  claim 49 , wherein the solution further comprises one or more cellular components from  Escherichia coli.    
     
     
         55 . The method of  claim 49 , wherein the uricase is a mammalian uricase. 
     
     
         56 . The method of  claim 49 , wherein the one or more cationic surfactants are added to a concentration of from 0.001% to 5.0%. 
     
     
         57 . The method of  claim 56 , wherein the one or more cationic surfactants are added to a concentration of from 0.01% to 0.5%. 
     
     
         58 . The method of  claim 56 , wherein the one or more cationic surfactants are added to a concentration of from 0.03% to 0.2%. 
     
     
         59 . The method of  claim 49 , wherein the solution is substantially free of polyanions, solid supports, and aggregates of the contaminating proteins. 
     
     
         60 . The method of  claim 49 , wherein the uricase protein has an isoelectric point greater than 7. 
     
     
         61 . A method for purifying a uricase comprising:
 (a) obtaining a solution comprising a mixture of a solubilized uricase, one or more solubilized contaminating proteins and an alkaline buffer, wherein the uricase is positively charged under alkaline pH and has an isoelectric point greater than or equal to 7 and the one or more contaminating proteins has a polyanion charge;   (b) contacting the solution comprising the mixture of the solubilized uricase and the one or more solubilized contaminating proteins with one or more cationic surfactants in an amount effective to preferentially precipitate the one or more contaminating proteins, thereby increasing the proportion of proteins remaining in solution represented by the uricase; and   (c) recovering the uricase in solution after the preferential precipitation of step (b);   wherein the uricase comprises at least 90% of the total protein in the solution;   wherein at least one of the one or more cationic surfactants is cetylpyridinium chloride; and   wherein the method is performed in the absence of a solid support.