8EL3

Light harvesting phycobiliprotein HaPE555 from the cryptophyte Hemiselmis andersenii CCMP644 in a loose interface filament

Summary for 8EL3

• Entry DOI: 10.2210/pdb8el3/pdb
• Descriptor: Phycoerythrin alpha-1 subunit, Phycoerythrin550 beta subunit, Phycoerythrin alpha-2 subunit, ... (6 entities in total)
• Functional Keywords: phycobiliprotein, antenna, light harvesting, cryptophyte, algae, globin, calm, carsp, photosynthesis, phycoerythrin, hemiselmis
• Biological source: Hemiselmis andersenii; More
• Total number of polymer chains: 12
• Total formula weight: 139992.28

Authors

Rathbone, H.W.,Michie, K.A.,Laos, A.L.,Curmi, P.M.G. (deposition date: 2022-09-23, release date: 2023-10-25, Last modification date: 2024-11-13)

Primary citation

Rathbone, H.W.,Laos, A.J.,Michie, K.A.,Iranmanesh, H.,Biazik, J.,Goodchild, S.C.,Thordarson, P.,Green, B.R.,Curmi, P.M.G.
Molecular dissection of the soluble photosynthetic antenna from the cryptophyte alga Hemiselmis andersenii.
Commun Biol, 6:1158-1158, 2023

PubMed Abstract: Cryptophyte algae have a unique phycobiliprotein light-harvesting antenna that fills a spectral gap in chlorophyll absorption from photosystems. However, it is unclear how the antenna transfers energy efficiently to these photosystems. We show that the cryptophyte Hemiselmis andersenii expresses an energetically complex antenna comprising three distinct spectrotypes of phycobiliprotein, each composed of two αβ protomers but with different quaternary structures arising from a diverse α subunit family. We report crystal structures of the major phycobiliprotein from each spectrotype. Two-thirds of the antenna consists of open quaternary form phycobiliproteins acting as primary photon acceptors. These are supplemented by a newly discovered open-braced form (~15%), where an insertion in the α subunit produces ~10 nm absorbance red-shift. The final components (~15%) are closed forms with a long wavelength spectral feature due to substitution of a single chromophore. This chromophore is present on only one β subunit where asymmetry is dictated by the corresponding α subunit. This chromophore creates spectral overlap with chlorophyll, thus bridging the energetic gap between the phycobiliprotein antenna and the photosystems. We propose that the macromolecular organization of the cryptophyte antenna consists of bulk open and open-braced forms that transfer excitations to photosystems via this bridging closed form phycobiliprotein.

PubMed: 37957226
DOI: 10.1038/s42003-023-05508-4

Experimental method

X-RAY DIFFRACTION (1.57 Å)