A PGK-neo vector was designed to replace exons 14-16, corresponding to bases 1499-1861 of the coding region. Sequence analysis revealed that the neo cassette was spliced out. The resulting transcript encoded an in-frame deletion of 126 amino acids at the N-terminus of the catalytic domain. This terminus contained one of the two divalent zinc binding sites. Since the deletion was in-frame, a mutant protein of approximately 75 kDa could be produced. (J:111662)