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The truncated hemoglobin from Mycobacterium leprae.
Paolo Visca1, Giulia Fabozzi, Andrea Petrucca
1Dipartimento di Biologia e Laboratorio Interdipartimentale di Microscopia Elettronica, Università Roma Tre, Viale G. Marconi 446, I-00146 Rome, Italy. visca@bio.uniroma3.it
Biochemical and Biophysical Research Communications
|June 21, 2002
Summary
This study characterizes Mycobacterium leprae truncated hemoglobin O (M. leprae trHbO), a novel O2 binding protein. Its structure and lower reactivity suggest adaptations to host defense mechanisms in leprosy.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Truncated hemoglobins (trHb's) are low molecular weight O2 binding proteins found in diverse organisms.
- A novel trHb, M. leprae trHbO, was identified from the Mycobacterium leprae genome.
Purpose of the Study:
- To investigate the structural and functional characteristics of M. leprae trHbO.
- To compare M. leprae trHbO with other truncated hemoglobins, particularly M. tuberculosis trHbN.
Main Methods:
- Sequence comparison and molecular modeling to predict M. leprae trHbO structure.
- Kinetic analysis of carbonylation rates to determine protein reactivity.
Main Results:
- M. leprae trHbO exhibits typical trHb structural features, including a compact alpha-helical fold and a ligand diffusion tunnel.
- The ferrous heme iron is hexacoordinated, similar to A. thaliana trHbO-3.
- M. leprae trHbO shows significantly lower carbonylation rates compared to M. tuberculosis trHbN.
Conclusions:
- The structural and kinetic properties of M. leprae trHbO suggest functional adaptations.
- Lower reactivity may confer resistance to reactive oxygen and nitrogen species produced by host phagocytic cells, potentially contributing to M. leprae survival.