The dppBCDF gene cluster of Haemophilus influenzae: Role in heme utilization.
BACKGROUND
Haemophilus influenzae requires a porphyrin source for aerobic growth and possesses multiple mechanisms to obtain this essential nutrient. This porphyrin requirement may be satisfied by either heme alone, or protoporphyrin IX in the presence of an iron source. One protein involved in heme acquisition by H. influenzae is the periplasmic heme binding protein HbpA. HbpA exhibits significant homology to the dipeptide and heme binding protein DppA of Escherichia coli. DppA is a component of the DppABCDF peptide-heme permease of E. coli. H. influenzae homologs of dppBCDF are located in the genome at a point distant from hbpA. The object of this study was to investigate the potential role of the H. influenzae dppBCDF locus in heme utilization.


RESULTS
An insertional mutation in dppC was constructed and the impact of the mutation on the utilization of both free heme and various proteinaceous heme sources as well as utilization of protoporphyrin IX was determined in growth curve studies. The dppC insertion mutant strain was significantly impacted in utilization of all tested heme sources and protoporphyin IX. Complementation of the dppC mutation with an intact dppCBDF gene cluster in trans corrected the growth defects seen in the dppC mutant strain.


CONCLUSIONS
The dppCBDF gene cluster constitutes part of the periplasmic heme-acquisition systems of H. influenzae.
Morton
Daniel J
DJ
Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA. dmorton@ouhsc.edu
Seale
Thomas W
TW
Vanwagoner
Timothy M
TM
Whitby
Paul W
PW
Stull
Terrence L
TL
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