Current limits of structural biology: The transient interaction between cytochrome c6 and photosystem I

  • Trimeric photosystem I from the cyanobacterium Thermosynechococcus elongatus (TePSI) is an intrinsic membrane protein, which converts solar energy into electrical energy by oxidizing the soluble redox mediator cytochrome c6 (Cyt c6) and reducing ferredoxin. Here, we use cryo-electron microscopy and small angle neutron scattering (SANS) to characterize the transient binding of Cyt c6 to TePSI. The structure of TePSI cross-linked to Cyt c6 was solved at a resolution of 2.9 Å and shows additional cofactors as well as side chain density for 84% of the peptide chain of subunit PsaK, revealing a hydrophobic, membrane intrinsic loop that enables binding of associated proteins. Due to the poor binding specificity, Cyt c6 could not be localized with certainty in our cryo-EM analysis. SANS measurements confirm that Cyt c6 does not bind to TePSI at protein concentrations comparable to those for cross-linking. However, SANS data indicate a complex formation between TePSI and the non-native mitochondrial cytochrome from horse heart (Cyt cHH). Our study pinpoints the difficulty of identifying very small binding partners (less than 5% of the overall size) in EM structures when binding affinities are poor. We relate our results to well resolved co-structures with known binding affinities and recommend confirmatory methods for complexes with KM values higher than 20 μM.

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Metadaten
Author:Adrian Kölsch, C. Radon, M. Golub, A. Baumert, Jörg Bürger, Thorsten Mielke, Fred LisdatORCiDGND, A. Feoktystov, J. Pieper, Athina ZouniORCiD, P. Wendler
URN:urn:nbn:de:kobv:526-opus4-13628
DOI:https://doi.org/10.1016/j.crstbi.2020.08.003
ISSN:2665-928X
Parent Title (English):Current Research in Structural Biology
Document Type:Article
Language:English
Year of Publication:2020
Publishing Institution:Technische Hochschule Wildau
Release Date:2021/01/08
Volume:2
First Page:171
Last Page:179
Source:Kölsch, A., Radon, C., Golub, M., Baumert, A., Bürger, J., Mielke, T., et al. (2020). Current limits of structural biology: The transient interaction between cytochrome c6 and photosystem I Current Research in Structural Biology. 2, 171-179.
Faculties an central facilities:Fachbereich Ingenieur- und Naturwissenschaften
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie
Licence (German):Creative Commons - CC BY-NC-ND - Namensnennung - Nicht kommerziell - Keine Bearbeitungen 4.0 International
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