Year: 2026
Type: article
Abstract: Photosystem I (PSI) exists in trimeric (tPSI) and monomeric (mPSI) forms within the thylakoid membrane of cyanobacteria. PSI functions as a light-driven electron pump, enabling the transfer of electrons from cytochrome c 6 (Cyt c 6 ) or plastocyanin to ferredoxin. Here, we have developed a novel protocol to obtain large amounts of intact, active mPSI from Thermosynechococcus vestitus ( Tv ) by dissociating highly purified tPSI using the detergent octaethylene glycol monododecyl ether (C 12 E 8 ) at elevated temperatures. We analysed the stability of the protein-detergent complex employing a combination of spectroscopic methods, such as fluorescence at 77 K and circular dichroism (CD), and investigated the detergent’s influence on delipidation and monomerisation. We determined the structure of mPSI to a resolution of 1.8 Å using cryogenic electron microscopy (cryo-EM). This structure retains all subunits except PsaL and we identified a sulfoquinovosyl diacylglycerol (SQD) molecule and 16 n-dodecyl ß-maltoside (βDM) molecules arranged in a ring around the complex. The mPSI structure was verified in solution at physiological temperature by applying small angle neutron scattering. Comparing the cofactor inventory of mPSI to that of tPSI, we suggest the assignment of a red-shifted chlorophyll pigment and discuss the influence of detergents and lipids on stability and oligomeric state of PSI. Finally, when adding native Tv Cyt c 6 under reducing conditions, additional density was observed in close proximity of the P 700 pigments, which indicates the presence of a transiently bound Cyt c 6 .
Source: Photosynthesis Research
Institutions: Humboldt-Universität zu Berlin, Uppsala University, Umeå Plant Science Centre, University of Otago, European Molecular Biology Laboratory, University of Tartu, Australian Nuclear Science and Technology Organisation, Australian Centre for Neutron Scattering, National Deuteration Facility, Johannes Kepler University of Linz
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,890
Funders: Australian Nuclear Science and Technology Organisation, Deutsche Forschungsgemeinschaft, Svenska Forskningsrådet Formas, Eesti Teadusagentuur, Knut och Alice Wallenbergs Stiftelse, Vetenskapsrådet, Umeå Universitet, Uppsala Universitet, Kempestiftelserna, Stockholms Universitet, Center for Exercise Medicine, University of Alabama at Birmingham
Awards: EXC 2008: Unifying Systems in Catalysis "UniSysCat", G2685071433, Grundläggande kunskap om karboxysomers biokemi med syftet att öka produktivitet hos framtida grödor, G3390287098, Boosting photosynthesis by mapping the interactome of the cyanobacterial CO2 fixing supercharger – the carboxysome, Boosting photosynthesis by mapping the interactome of the cyanobacterial CO2 fixing supercharger – the carboxysome, G8136362559
OpenAlex ID: W7222268030