A redox switch allows binding of ferrous and ferric ions in the cyanobacterial iron binding protein FutA from Prochlorococcus

Bolton, Rachel, Machelett, Moritz M., Stubbs, Jack, Axford, Danny, Caramello, Nicolas, Catapano, Lucrezia, Malý, Martin, Rodrigues, Matthew J., Cordery, Charlotte, Tizzard, Graham J., MacMillan, Fraser ORCID: https://orcid.org/0000-0002-2410-4790, Engilberge, Sylvain, von Stetten, David, Tosha, Takehiko, Sugimoto, Hiroshi, Worrall, Jonathan A. R., Webb, Jeremy S., Zubkov, Mike, Coles, Simon, Mathieu, Eric, Steiner, Roberto A., Murshudov, Garib, Schrader, Tobias E., Orville, Allen M., Royant, Antoine, Evans, Gwyndaf, Hough, Michael A., Owen, Robin L. and Tews, Ivo (2024) A redox switch allows binding of ferrous and ferric ions in the cyanobacterial iron binding protein FutA from Prochlorococcus. Proceedings of the National Academy of Sciences of the United States of America, 121 (12). ISSN 0027-8424

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Abstract

The marine cyanobacterium Prochlorococcus is a main contributor to global photosynthesis, whilst being limited by iron availability. Cyanobacterial genomes typically encode two different types of FutA iron binding proteins: periplasmic FutA2 ABC transporter subunits bind ferric (Fe3+), while cytosolic FutA1 binds ferrous (Fe2+). Owing to their small size and their economized genome Prochlorococcus ecotypes typically possess a single futA 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 solvent molecule coordinate iron in trigonal bipyramidal geometry. Positioning of the positively charged Arg103 side chain in the second coordination shell was consistent with an overall charge-neutral ferric 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 ferrous binding state; here, an additional positioning of the Arg203 side chain in the second coordination shell maintained an overall charge neutral ferrous binding site. Room temperature dose series using serial synchrotron crystallography and an XFEL X-ray pump-probe approach capture the transition between ferric and ferrous states, revealing how Arg203 operates as a switch to accommodate the different iron oxidation states. This switching ability of the Prochlorococcus FutA protein may reflect ecological adaptation by genome streamlining and loss of specialized FutA proteins.

Item Type:	Article
Additional Information:	Data, Materials, and Software Availability: SI accompanies this submission. Protein Structure data have been deposited in PDB under accession codes (8OEM, 8RK1, 8OGG, 8OEI, 8C4Y). Raw data are available at https://doi.org/10.5281/zenodo.10732657. Financial support: Japan Partnering Award, Biological Sciences Research Council (BBSRC) BB/R021015/1, BB/W001950/1 to J.S.W., MA.H., and R.L.O.; Diamond Doctoral Studentship Programme to R.B., J.S., M.J.R., and C.C.; South Coast Biosciences Doctoral Training Partnership SoCoBio DTP BBSRC BB/T008768/1 to J.S.; PhD studentships by Hamburg University and the European Synchrotron Radiation Facility (ESRF) to N.C., the Collaborative Computing Project 4 (CCP4) to L.C. (#7920S22020007); the Institute for Life Sciences (Southampton) to C.C.; BBSRC BB/X002950/1 “The National Biofilms Innovation Centre (NBIC)” to J.S.W.; Wellcome Investigator Award 210734/Z/18/Z to A.M.O.; Royal Society Wolfson Fellowship RSWF\R2\182017 to A.M.O. We acknowledge facility access to the National Crystallography Service (NCS) Southampton; DLS MX15722, NT14493, NT23570; SACLA 2022A8002, 2022B8041; Forschungsreaktor München ID:16106; ESRF BM07-FIP2 and icOS, MX2373, MX2374; Diamond Light Source (DLS) UK XFEL hub and ESRF for travel support.
Uncontrolled Keywords:	sdg 14 - life below water ,/dk/atira/pure/sustainabledevelopmentgoals/life_below_water
Faculty \ School:	Faculty of Science > School of Chemistry (former - to 2024)
UEA Research Groups:	Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry Faculty of Science > Research Groups > Chemistry of Life Processes Faculty of Science > Research Groups > Chemistry of Light and Energy
Depositing User:	LivePure Connector
Date Deposited:	04 Mar 2024 18:34
Last Modified:	25 Sep 2024 17:40
URI:	https://ueaeprints.uea.ac.uk/id/eprint/94506
DOI:	10.1101/2023.05.23.541926

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