8OEM

Crystal structure of FutA bound to Fe(II)

Summary for 8OEM

• Entry DOI: 10.2210/pdb8oem/pdb
• Descriptor: Putative iron ABC transporter, substrate binding protein, FE (II) ION (3 entities in total)
• Functional Keywords: periplasmic iron-binding protein, metal ion binding, iron homeostasis, metal binding protein
• Biological source: Prochlorococcus marinus subsp. pastoris str. CCMP1986
• Total number of polymer chains: 1
• Total formula weight: 35275.09

Authors

Bolton, R.,Tews, I. (deposition date: 2023-03-10, release date: 2023-08-30, Last modification date: 2024-03-27)

Primary citation

Bolton, R.,Machelett, M.M.,Stubbs, J.,Axford, D.,Caramello, N.,Catapano, L.,Maly, M.,Rodrigues, M.J.,Cordery, C.,Tizzard, G.J.,MacMillan, F.,Engilberge, S.,von Stetten, D.,Tosha, T.,Sugimoto, H.,Worrall, J.A.R.,Webb, J.S.,Zubkov, M.,Coles, S.,Mathieu, E.,Steiner, R.A.,Murshudov, G.,Schrader, T.E.,Orville, A.M.,Royant, A.,Evans, G.,Hough, M.A.,Owen, R.L.,Tews, I.
A redox switch allows binding of Fe(II) and Fe(III) ions in the cyanobacterial iron-binding protein FutA from Prochlorococcus.
Proc.Natl.Acad.Sci.USA, 121:e2308478121-e2308478121, 2024

PubMed Abstract: The marine cyanobacterium is a main contributor to global photosynthesis, whilst being limited by iron availability. Cyanobacterial genomes generally encode two different types of FutA iron-binding proteins: periplasmic FutA2 ABC transporter subunits bind Fe(III), while cytosolic FutA1 binds Fe(II). Owing to their small size and their economized genome ecotypes typically possess a single gene. How the encoded FutA protein might bind different Fe oxidation states was previously unknown. Here, we use structural biology techniques at room temperature to probe the dynamic behavior of FutA. Neutron diffraction confirmed four negatively charged tyrosinates, that together with a neutral water molecule coordinate iron in trigonal bipyramidal geometry. Positioning of the positively charged Arg103 side chain in the second coordination shell yields an overall charge-neutral Fe(III) binding state in structures determined by neutron diffraction and serial femtosecond crystallography. Conventional rotation X-ray crystallography using a home source revealed X-ray-induced photoreduction of the iron center with observation of the Fe(II) binding state; here, an additional positioning of the Arg203 side chain in the second coordination shell maintained an overall charge neutral Fe(II) binding site. Dose series using serial synchrotron crystallography and an XFEL X-ray pump-probe approach capture the transition between Fe(III) and Fe(II) states, revealing how Arg203 operates as a switch to accommodate the different iron oxidation states. This switching ability of the FutA protein may reflect ecological adaptation by genome streamlining and loss of specialized FutA proteins.

PubMed: 38489389
DOI: 10.1073/pnas.2308478121

Experimental method

X-RAY DIFFRACTION (1.7 Å)