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Science. 2015 Jan 30;347(6221):551-5. doi: 10.1126/science.aaa1534.

Protein structure. Structure and activity of tryptophan-rich TSPO proteins.

Author information

1
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
2
The New York Consortium on Membrane Protein Structure (NYCOMPS), New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA.
3
The New York Consortium on Membrane Protein Structure (NYCOMPS), New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA. New York Structural Biology Center, Synchrotron Beamlines, Brookhaven National Laboratory, Upton, NY 11973, USA.
4
The New York Consortium on Membrane Protein Structure (NYCOMPS), New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA. Department of Informatics, Bioinformatics and Computational Biology, Technische Universität München, Garching 85748, Germany.
5
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA. The New York Consortium on Membrane Protein Structure (NYCOMPS), New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA. New York Structural Biology Center, Synchrotron Beamlines, Brookhaven National Laboratory, Upton, NY 11973, USA. Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA. wayne@xtl.cumc.columbia.edu.

Abstract

Translocator proteins (TSPOs) bind steroids and porphyrins, and they are implicated in many human diseases, for which they serve as biomarkers and therapeutic targets. TSPOs have tryptophan-rich sequences that are highly conserved from bacteria to mammals. Here we report crystal structures for Bacillus cereus TSPO (BcTSPO) down to 1.7 Å resolution, including a complex with the benzodiazepine-like inhibitor PK11195. We also describe BcTSPO-mediated protoporphyrin IX (PpIX) reactions, including catalytic degradation to a previously undescribed heme derivative. We used structure-inspired mutations to investigate reaction mechanisms, and we showed that TSPOs from Xenopus and man have similar PpIX-directed activities. Although TSPOs have been regarded as transporters, the catalytic activity in PpIX degradation suggests physiological importance for TSPOs in protection against oxidative stress.

PMID:
25635100
PMCID:
PMC4341906
DOI:
10.1126/science.aaa1534
[Indexed for MEDLINE]
Free PMC Article

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