Identification of an EF-Tu protein that is periplasm-associated and processed in Neisseria gonorrhoeae

A 44 kDa protein is a dominant component of periplasmic extracts of Neisseria gonorrhoeae. Peptide sequence generated from a cyanogen-bromide-cleaved fragment of this protein indicated sequence homology with elongation factor-Tu (EF-Tu). Polyclonal antiserum was made against the 44 kDa protein purified from periplasm extracts of N. gonorrhoeae. The preabsorbed antiserum was immunoblotted against whole-cell lysates on two-dimensional gels. A 44 kDa protein and a smaller 37 kDa protein were recognized by this antiserum. A N. gonorrhoeae lambda phage DNA library was screened and a clone expressing a 44 kDa protein was identified. The DNA insert in this clone contained several genes homologous to genes contained in the str operon of Escherichia coli. One ORF product with a calculated molecular mass of 43 kDa was highly homologous to the EF-TuA of E. coli. A synthetic peptide antiserum specific for a portion of the C terminus of EF-Tu confirmed that the 37 kDa protein in whole-cell lysates of N. gonorrhoeae was a processed form of EF-Tu. Deletion of the tufA gene homologue in N. gonorrhoeae was attempted but was unsuccessful.