Immobilization and single-step purification of fusion proteins using DEAE-cellulose.

We have developed a new single-step system, using a DEAE matrix, to immobilize and/or purify fusion proteins containing the choline-binding domain of the Streptococcus pneumoniae murein hydrolases. We have constructed a choline-binding-domain--beta-galactosidase chimera, which can be purified by this procedure and shows a high beta-galactosidase activity when immobilized in the column. A vector plasmid, pCUZ1, containing the lppp-5/lac promoter as well as 13 restriction sites, was constructed to facilitate the cloning and expression of gene fusions. This plasmid also allows the selection of recombinants by the well-known blue/white 5-bromo-4-chloro-3-indolyl-beta-D-galactoside procedure. A chimera between the choline-binding domain and the pneumococcal hemolysin was also constructed and purified using pCUZ1.