EXPRESSION IN ESCHERICHIA-COLI OF THE PUTATIVE N-ACETYLNEURAMINATE LYASE GENE (NANA) FROM HAEMOPHILUS-INFLUENZAE - OVERPRODUCTION, PURIFICATION, AND CRYSTALLIZATION

The cloning and expression of the Haemophilus influenzae gene, nanA, f or the putative N-acetylneuraminate lyase enzyme, also known as N-acet ylneuraminic acid aldolase or sialic acid aldolase, are reported. The gene was isolated from ATCC type strain 49247 and cloned into the Esch erichia coli expression vector pKKtac, which contained the strong tac promoter. Gene expression was compared with the homologous E. coli npl gene coding for the lyase. Purification protocols for the products of the nanA and npL genes are presented. Activity analysis showed that t he nanA gene product is a sialic acid aldolase with more than threefol d greater specific activity (6.9 IU/mg) than the enzyme from E. coli ( less than or equal to 2 IU/mg). A method for the provision of lyase or thorhombic crystals is reported. These crystals diffract to better tha n 2.0 Angstrom, which paves the way to the solution of the enzyme's th ree-dimensional structure. (C) 1998 Academic Press.