Process for purification of water soluble penicillin binding protein 2a

A process for isolating in substantially purified form water soluble penicillin binding protein 2a from a biological cell comprising:

• a) lysing said cell;
• b) fractionating the cell lysate to obtain a proteinaceous solution substantially free from cellular debris;
• c) contacting, at a pH of about 8, the proteinaceous solution obtained in b) with an anion-exchange resin that is not capable of binding the water soluble penicillin binding protein 2a contained in the proteinaceous solution;
• d) collecting water soluble penicillin binding protein 2a-containing fractions of the solution that do not bind to the anion-exchange resin;
• e) contacting, at a pH of about 6, the water soluble penicillin binding protein 2a-containing fractions of d) with a cation-exchange resin capable of binding the water soluble penicillin binding protein 2a;
• f) eluting the water soluble penicillin binding protein 2a from the cation-exchange resin with a linear salt gradient;
• g) concentrating and diluting the eluate of step f) to reduce salt concentration;
• h) contacting, at a pH of about 8, the eluate obtained in g) with a dye-ligand resin selected from the group consisting of Reactive Blue 4, Reactive Green 5, Reactive Green 19, Reactive Red 120, Reactive Brown 10, Reactive Blue 72, Matrex.TM. Blue A, Matrex.TM. Blue B, Matrex.TM. Red A, and Matrex.TM. Green A;
• and
• i) eluting the water soluble penicillin binding protein 2a from the dye-ligand resin with a linear salt gradient.