7RK0

Crystal structure of Thermovibrio ammonificans THI4

Summary for 7RK0

• Entry DOI: 10.2210/pdb7rk0/pdb
• Descriptor: Thiamine thiazole synthase, FE (III) ION, 2-[(E)-[(4R)-5-[[[(2R,3S,4R,5R)-5-(6-aminopurin-9-yl)-3,4-bis(oxidanyl)oxolan-2-yl]methoxy-oxidanyl-phosphoryl]oxy-oxidanyl-phosphoryl]oxy-4-oxidanyl-3-oxidanylidene-pentan-2-ylidene]amino]ethanoic acid, ... (4 entities in total)
• Functional Keywords: suicide enzyme, thiamin, thiazole, biosynthetic protein
• Biological source: Thermovibrio ammonificans
• Total number of polymer chains: 4
• Total formula weight: 117681.08

Authors

Li, Q.,Bruner, S.D. (deposition date: 2021-07-21, release date: 2021-09-01, Last modification date: 2023-10-18)

Primary citation

Joshi, J.,Li, Q.,Garcia-Garcia, J.D.,Leong, B.J.,Hu, Y.,Bruner, S.D.,Hanson, A.D.
Structure and function of aerotolerant, multiple-turnover THI4 thiazole synthases.
Biochem.J., 478:3265-3279, 2021

PubMed Abstract: Plant and fungal THI4 thiazole synthases produce the thiamin thiazole moiety in aerobic conditions via a single-turnover suicide reaction that uses an active-site Cys residue as sulfur donor. Multiple-turnover (i.e. catalytic) THI4s lacking an active-site Cys (non-Cys THI4s) that use sulfide as sulfur donor have been biochemically characterized -- but only from archaeal methanogens that are anaerobic, O2-sensitive hyperthermophiles from sulfide-rich habitats. These THI4s prefer iron as cofactor. A survey of prokaryote genomes uncovered non-Cys THI4s in aerobic mesophiles from sulfide-poor habitats, suggesting that multiple-turnover THI4 operation is possible in aerobic, mild, low-sulfide conditions. This was confirmed by testing 23 representative non-Cys THI4s for complementation of an Escherichia coli ΔthiG thiazole auxotroph in aerobic conditions. Sixteen were clearly active, and more so when intracellular sulfide level was raised by supplying Cys, demonstrating catalytic function in the presence of O2 at mild temperatures and indicating use of sulfide or a sulfide metabolite as sulfur donor. Comparative genomic evidence linked non-Cys THI4s with proteins from families that bind, transport, or metabolize cobalt or other heavy metals. The crystal structure of the aerotolerant bacterial Thermovibrio ammonificans THI4 was determined to probe the molecular basis of aerotolerance. The structure suggested no large deviations compared with the structures of THI4s from O2-sensitive methanogens, but is consistent with an alternative catalytic metal. Together with complementation data, use of cobalt rather than iron was supported. We conclude that catalytic THI4s can indeed operate aerobically and that the metal cofactor inserted is a likely natural determinant of aerotolerance.

PubMed: 34409984
DOI: 10.1042/BCJ20210565

Experimental method

X-RAY DIFFRACTION (2.28 Å)