Characterization of protonmotive force generation in liposomes reconstituted from phosphatidylethanolamine, reaction centers with light-harvesting complexes isolated from Rhodopseudomonas palustris

Biochemistry ◽  
1988 ◽  
Vol 27 (6) ◽  
pp. 2014-2023 ◽  
Author(s):  
Douwe Molenaar ◽  
Wim Crielaard ◽  
Klaas J. Hellingwerf
Keyword(s):  
Light Harvesting ◽  
Rhodopseudomonas Palustris ◽  
Reaction Centers ◽  
Force Generation ◽  
Protonmotive Force ◽  
Light Harvesting Complexes

scholarly journals The terminal phycobilisome emitter, LCM: A light-harvesting pigment with a phytochrome chromophore

2015 ◽  
Vol 112 (52) ◽  
pp. 15880-15885 ◽  
Author(s):  
Kun Tang ◽  
Wen-Long Ding ◽  
Astrid Höppner ◽  
Cheng Zhao ◽  
Lun Zhang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Transient Absorption ◽  
Light Harvesting ◽  
Reaction Centers ◽  
Protein Fold ◽  
Light Harvesting Complexes ◽  
Exciton Coupling ◽  
Femtosecond Transient Absorption ◽  
Orange Carotenoid Protein ◽  
Sensory Photoreceptors

Photosynthesis relies on energy transfer from light-harvesting complexes to reaction centers. Phycobilisomes, the light-harvesting antennas in cyanobacteria and red algae, attach to the membrane via the multidomain core-membrane linker, LCM. The chromophore domain of LCM forms a bottleneck for funneling the harvested energy either productively to reaction centers or, in case of light overload, to quenchers like orange carotenoid protein (OCP) that prevent photodamage. The crystal structure of the solubly modified chromophore domain from Nostoc sp. PCC7120 was resolved at 2.2 Å. Although its protein fold is similar to the protein folds of phycobiliproteins, the phycocyanobilin (PCB) chromophore adopts ZZZssa geometry, which is unknown among phycobiliproteins but characteristic for sensory photoreceptors (phytochromes and cyanobacteriochromes). However, chromophore photoisomerization is inhibited in LCM by tight packing. The ZZZssa geometry of the chromophore and π-π stacking with a neighboring Trp account for the functionally relevant extreme spectral red shift of LCM. Exciton coupling is excluded by the large distance between two PCBs in a homodimer and by preservation of the spectral features in monomers. The structure also indicates a distinct flexibility that could be involved in quenching. The conclusions from the crystal structure are supported by femtosecond transient absorption spectra in solution.

scholarly journals Light’s interaction with pigments in chloroplasts: The murburn perspective, with special relevance to carotenoids

2020 ◽  
Author(s):  
Kelath Murali Manoj ◽  
Afsal Manekkathodi
Keyword(s):  
Light Harvesting ◽  
Reaction Centers ◽  
Oxygenic Photosynthesis ◽  
Physiological Data ◽  
Light Harvesting Complexes ◽  
Light Reaction ◽  
Historical Perspectives ◽  
Electron Emitters ◽  
Theoretical Foundations ◽  
Special Relevance

The prevailing understanding on photolytic photophosphorylation, the light reaction of oxygenic photosynthesis, considers the vast majority of the diverse pigments, chlorophyll binding proteins (CBPs) and light harvesting complexes (LHCs) as photon-energy relaying facets; only the two photosystems’ (PS) reaction centers’ chlorophyll a couplets are deemed to serve as photo-excitable electron emitters. Highlighting the historical perspectives involved, we present reasons why this conventional perception is unmet by theoretical foundations, unsupported by molecular awareness on the various pigments and unverified by physiological data available on chloroplasts. Further, we propose a simple diffusible reactive oxygen species (DROS)-based mechanism for correlating the functions of various light harvesting LHCs and CBPs with the reaction centers of PS I & II.

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