3IS7

Structure of mineralized Bfrb from Pseudomonas aeruginosa to 2.1A Resolution

Summary for 3IS7

• Entry DOI: 10.2210/pdb3is7/pdb
• Related: 3IS8 3ISE 3ISF
• Descriptor: Bacterioferritin, PROTOPORPHYRIN IX CONTAINING FE, POTASSIUM ION, ... (4 entities in total)
• Functional Keywords: electron transport; iron storage, heme, iron, iron storage, metal-binding, electron transport
• Biological source: Pseudomonas aeruginosa
• Total number of polymer chains: 24
• Total formula weight: 453556.46

Authors

Lovell, S.,Weeratunga, S.K.,Battaile, K.P.,Rivera, M. (deposition date: 2009-08-25, release date: 2010-02-02, Last modification date: 2023-09-06)

Primary citation

Weeratunga, S.K.,Lovell, S.,Yao, H.,Battaile, K.P.,Fischer, C.J.,Gee, C.E.,Rivera, M.
Structural Studies of Bacterioferritin B from Pseudomonas aeruginosa Suggest a Gating Mechanism for Iron Uptake via the Ferroxidase Center
Biochemistry, 49:1160-1175, 2010

PubMed Abstract: The structure of recombinant Pseudomonas aeruginosa bacterioferritin B (Pa BfrB) has been determined from crystals grown from protein devoid of core mineral iron (as-isolated) and from protein mineralized with approximately 600 iron atoms (mineralized). Structures were also obtained from crystals grown from mineralized BfrB after they had been soaked in an FeSO(4) solution (Fe soak) and in separate experiments after they had been soaked in an FeSO(4) solution followed by a soak in a crystallization solution (double soak). Although the structures consist of a typical bacterioferritin fold comprised of a nearly spherical 24-mer assembly that binds 12 heme molecules, comparison of microenvironments observed in the distinct structures provided interesting insights. The ferroxidase center in the as-isolated, mineralized, and double-soak structures is empty. The ferroxidase ligands (except His130) are poised to bind iron with minimal conformational changes. The His130 side chain, on the other hand, must rotate toward the ferroxidase center to coordinate iron. In comparison, the structure obtained from crystals soaked in an FeSO(4) solution displays a fully occupied ferroxidase center and iron bound to the internal, Fe((in)), and external, Fe((out)), surfaces of Pa BfrB. The conformation of His130 in this structure is rotated toward the ferroxidase center and coordinates an iron ion. The structures also revealed a pore on the surface of Pa BfrB that likely serves as a port of entry for Fe(2+) to the ferroxidase center. On its opposite end, the pore is capped by the side chain of His130 when it adopts its "gate-closed" conformation that enables coordination to a ferroxidase iron. A change to its "gate-open", noncoordinative conformation creates a path for the translocation of iron from the ferroxidase center to the interior cavity. These structural observations, together with findings obtained from iron incorporation measurements in solution, suggest that the ferroxidase pore is the dominant entry route for the uptake of iron by Pa BfrB. These findings, which are clearly distinct from those made with Escherichia coli Bfr [Crow, A. C., Lawson, T. L., Lewin, A., Moore, G. R., and Le Brun, N. E. (2009) J. Am. Chem. Soc. 131, 6808-6813], indicate that not all bacterioferritins operate in the same manner.

PubMed: 20067302
DOI: 10.1021/bi9015204

Experimental method

X-RAY DIFFRACTION (2.1 Å)