Complementation of a truncated membrane-bound Enzyme IINag from Klebsiella pneumoniae with a soluble Enzyme III in Escherichia coli K12.

Cloning and analysis of the gene nagE encoding Enzyme IINag (EIINag) from Klebsiella pneumoniae revealed strong similarities with the corresponding gene from Escherichia coli K12. Truncated EIINag proteins were generated by inserting a series of Tn1725 transposons into the structural gene; the positions of the insertions were mapped by restriction enzyme analysis, and the activity of the polypeptides determined by in vitro and in vivo tests. Insertions in the region encoding the amino-terminal half of the protein invariably abolished transport and phosphorylation activity, while truncated proteins lacking a C-terminal domain homologous to the soluble Enzyme III (crr gene) could be complemented by this molecule to nearly wild-type activity.