Expression of the GTPase activating domain of the neurofibromatosis type 1 (NF1) gene in Escherichia coli and role of the conserved lysine residue.

A small catalytic domain from the neurofibromatosis type 1 gene, NF1-333, consisting of 333 amino acids between residues 1197 and 1528, including an additional N-terminal methionine, was expressed in Escherichia coli as a soluble protein. Its catalytic activity under non-saturating conditions is similar to the full-length p120-GAP but different from truncated GAP-334. Under saturating conditions its kcat and KM are lower. Lys-1422, which is totally conserved in all GAP proteins, was mutated and the properties of the mutant protein investigated. Lys-1422 seems to be essential for the stability of the proteins and not for its catalytic activity.