A RAPID METHOD FOR THE PURIFICATION OF LARGE AMOUNTS OF AN ALPHA-COMPLEMENTING PEPTIDE DERIVED FROM BETA-GALACTOSIDASE (ESCHERICHIA-COLI)

A DNA segment coding for residues 6-44 of beta-galactosidase was ligat ed to a vector with the glutathione-S-transferase gene which also cont ained a sequence coding for a thrombin recognition site. The fused pro tein, with an additional 9 amino acids coded for by the vector, was pu rified using a glutathione agarose affinity column. A peptide made up of residues 6-44 of beta-galactosidase and the 9 additional amino acid s was then cleaved from the glutathione-S-transferase using thrombin a nd purified with a gel filtration column. The peptide was about 3-4 ti mes as active for alpha-complementation as the alpha-peptide derived f rom CNBr digestion of wild type beta-galactosidase.