7t7u
Light Harvesting complex phycocyanin PC 630, from the cryptophyte Chroomonas sp. M1627
Structural highlights
FunctionA0A067XP78_9CRYP Light-harvesting photosynthetic tetrapyrrole chromophore-protein from the phycobiliprotein complex.[ARBA:ARBA00033724] Publication Abstract from PubMedIn addition to their membrane-bound chlorophyll a/c light-harvesting antenna, the cryptophyte algae have evolved a unique phycobiliprotein antenna system located in the thylakoid lumen. The basic unit of this antenna consists of two copies of an alphabeta protomer where the alpha and beta subunits scaffold different combinations of a limited number of linear tetrapyrrole chromophores. While the beta subunit is highly conserved, encoded by a single plastid gene, the nuclear-encoded alpha subunits have evolved diversified multigene families. It is still unclear how this sequence diversity results in the spectral diversity of the mature proteins. By careful examination of three newly-determined crystal structures in comparison with three previously obtained, we show how the alpha subunit amino acid sequences control chromophore conformations and hence spectral properties even when the chromophores are identical. Previously we have shown that alpha subunits control the quaternary structure of the mature alphabeta.alphabeta complex (either open or closed), however, each species appeared to only harbor a single quaternary form. Here we show that species of the Hemiselmis genus contain expressed alpha subunit genes that encode both distinct quaternary structures. Finally, we have discovered a common single-copy gene (expressed into protein) consisting of tandem copies of a small alpha subunit that could potentially scaffold pairs of light harvesting units. Together, our results show how the diversity of the multigene alpha subunit family produces a range of mature cryptophyte antenna proteins with differing spectral properties, and the potential for minor forms that could contribute to acclimation to varying light regimes. This article is protected by copyright. All rights reserved. Molecular structures reveal the origin of spectral variation in cryptophyte light harvesting antenna proteins.,Michie KA, Harrop SJ, Rathbone HW, Wilk KE, Teng CY, Hoef-Emden K, Hiller RG, Green BR, Curmi PMG Protein Sci. 2023 Jan 31:e4586. doi: 10.1002/pro.4586. PMID:36721353[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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