The singular properties of photosynthetic cytochrome c₅₅₀ from the diatom Phaeodactylum tricornutum suggest new alternative functions

Abstract

Cytochrome c550 is an extrinsic component in the luminal side of photosystem II (PSII) in cyanobacteria, as well as in eukaryotic algae from the red photosynthetic lineage including, among others, diatoms. We have established that cytochrome c550 from the diatom Phaeodactylum tricornutum can be obtained as a complete protein from the membrane fraction of the alga, although a C‐terminal truncated form is purified from the soluble fractions of this diatom as well as from other eukaryotic algae. Eukaryotic cytochromes c550 show distinctive electrostatic features as compared with cyanobacterial cytochrome c550. In addition, co‐immunoseparation and mass spectrometry experiments, as well as immunoelectron microscopy analyses, indicate that although cytochrome c550 from P. tricornutum is mainly located in the thylakoid domain of the chloroplast – where it interacts with PSII – , it can also be found in the chloroplast pyrenoid, related with proteins linked to the CO2 concentrating mechanism and assimilation. These results thus suggest new alternative functions of this heme protein in eukaryotes.

Photosynthesis—European Congress on Photosynthesis Research

“…The articles in this Special Issue range from original articles applying sophisticated biophysical methods (Yakovlev et al , Sipka et al , Capone et al ) and theoretical and experimental consideration on the water‐splitting complex (Capone et al 2019, Yamaguchi et al , Chatterjee et al ) and photosystem I (Santabarbara et al ) to more integrated aspects of photosynthesis research (Buezo et al , Hamdani et al , Ptushenko and Ptushenko , Hernández‐Prieto et al , Krieger‐Liszkay et al ). A number of articles treat regulatory aspects of photosystem II (Shevela et al ), the plastoquinone pool (Borisova‐Mubarakshina et al ), cytochrome c (Bernal‐Bayard et al ), redox regulation (Nikkanen et al ), photoacclimation (Hu et al ) and photorespiration (García‐Caledrón et al ). The growing interest in structural aspects is shown by articles on the dynamics of the thylakoid membrane (Solovchenko et al , Konert et al , Ughy et al ) and of specific proteins (Carius et al , Vojta and Fulgosi ), protein complexes (Kuthanová Trsková et al , Fedorov et al ) and the antenna (Albanese et al , Kuthanová Trsková et al 2019).…”

Towards a biochemical characterization of the diatom pyrenoid

“…It was demonstrated that PtLCIB3 functions in stabilizing the pH environment of photosystem components as well as supply CO2 to the pyrenoid (Jin et al, 2016;Kikutani et al, 2016). The heme protein cytochrome c550, which interacts with the PSII, has also been found to localize to the pyrenoid as shown from co-immunoprecipitation and immunogold labelling experiments (Bernal-Bayard et al, 2019). Other than the above-mentioned works, there is currently no known studies on the exact protein compositions that make up the diatom pyrenoid and data on protein-protein interactions remains elusive.…”