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Heme binding to Leishmania mexicana amazonensis
1Rockefeller University Hospital, New York, NY 10021.
Molecular and Biochemical Parasitology
|May 1, 1988
Summary
Leishmania mexicana amazonensis parasites require external heme for growth due to a deficiency. This study reveals specific heme binding sites on parasites, potentially regulated by growth phase.
Area of Science:
- Parasitology
- Molecular Biology
- Biochemistry
Background:
- Leishmania mexicana amazonensis is a pathogenic parasite.
- Its growth is heme-dependent due to a biosynthetic deficiency.
Purpose of the Study:
- To investigate the mechanism of exogenous heme uptake in Leishmania mexicana amazonensis.
- To characterize the binding kinetics and regulation of heme uptake.
Main Methods:
- Utilized [55Fe]hemin to study heme binding to cultured promastigotes.
- Investigated binding equilibrium, dissociation, pH effects, and metalloporphyrin displacement.
- Employed Scatchard analysis to determine binding affinity and site number.
Main Results:
- Heme binding reached equilibrium within 6 hours at 4°C and was pH-sensitive.
- Scatchard analysis indicated a high-affinity interaction (0.03 nM-1) with approximately 400 binding sites per promastigote.
- Heme binding increased ~10-fold in logarithmic growth phase compared to stationary phase, primarily due to more binding sites.
Conclusions:
- Leishmania mexicana amazonensis promastigotes exhibit specific heme binding, suggesting a receptor-mediated process.
- Heme binding appears to be regulated by the parasite's growth phase, with increased uptake during logarithmic growth.