ELEMENTAL IRON DOES REPRESS TRANSFERRIN, HEMOPEXIN AND HEMOGLOBIN RECEPTOR EXPRESSION IN HAEMOPHILUS-INFLUENZAE

The iron repressible nature of Haemophilus influenzae transferrin bind ing proteins suggests a regulatory role for elemental iron in their ex pression. The existence of a Haemophilus ferric uptake repressor (Fur) binding motif identified in the promoter region of both rbpA and rbpB further supports this hypothesis. However, a recent study using brain heart infusion growth medium suggested that transferrin binding prote in synthesis in H. influenzae was haem- rather than iron-regulated. Th e present study re-investigates this observation and using a chemicall y defined medium, we demonstrate that elemental iron haem or protoporp hyrin IX can each regulate Haemophilus influenzae transferrin, haemope xin and haemoglobin receptor expression.