IDENTIFICATION AND PURIFICATION OF A HEMOGLOBIN-BINDING OUTER-MEMBRANE PROTEIN FROM NEISSERIA-GONORRHOEAE

The majority of in vitro-grown Neisseria gonorrhoeae strains were unab le to use hemoglobin as the sole source of iron for growth (Hgb(-)), b ut a minor population was able to do so (Hgb(+)), The ability of Hgb() gonococci to utilize hemoglobin as the iron source was associated wi th the expression of an iron-repressible 89-kDa hemoglobin-binding pro tein in the outer membrane. The N-terminal amino acid sequence of this protein revealed amino acids, from positions 2 to 16, identical to th ose of HpuB, an 85 kDa iron-regulated hemoglobin-haptoglobin utilizati on outer membrane protein of Neisseria meningitidis, Isogenic mutants constructed by allelic replacement with a meningococcal hpu::mini-Tn3e rm construct no longer expressed the 89-kDa protein. Mutants could not utilize hemoglobin to support growth but still grew on heme. Thus, th e gonococcal HpuB homolog is a functional hemoglobin receptor and is e ssential for growth with hemoglobin.