Mutational analysis of the structure basis for the multimerization function of NifA central domain

In Klebsiella pneumoniae (Kp) NifA central domain, when the conservative am ino acid residue Thr-290 in C3 region was replaced by Val, the function of NifA for activating the transcription of nif genes was lost. Thus the conse rvative Thr-290 residue seems critical for the activation function of NifA central domain. This point mutant of NifA central domain is used to examine the putative multimerization function of NifA central domain by merodiploi d experiment. The results showed that the NifA central domain bore the mult imerization determinants of NifA protein. A series of truncated mutants of NifA were constructed to determine the structural elements at the central d omain critical for multimerization. It demonstrates that amino acid residue s 252-453 are involved in the multimerization function of NifA central doma in.