4ryi | pdb_00004ryi
Crystal structure of BcTSPO/PK11195 complex
Structural highlights
FunctionTSPO_BACCR Binds tetrapyrroles and promotes the photooxidative degradation of protoporphyrin IX (PubMed:25635100). Can bind the benzodiazepine receptor agonist PK-11195 (in vitro); this interferes with photooxidative tetrapyrrole degradation (PubMed:25635100). May play a role in the transmembrane transport of tetrapyrroles and similar compounds (By similarity).[UniProtKB:Q9RFC8][1] Publication Abstract from PubMedTranslocator 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 A 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. Protein structure. Structure and activity of tryptophan-rich TSPO proteins.,Guo Y, Kalathur RC, Liu Q, Kloss B, Bruni R, Ginter C, Kloppmann E, Rost B, Hendrickson WA Science. 2015 Jan 30;347(6221):551-5. doi: 10.1126/science.aaa1534. PMID:25635100[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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