7yk5
Rubisco from Phaeodactylum tricornutum bound to PYCO1(452-592)
Structural highlights
FunctionE9PAI6_PHATR RuBisCO catalyzes two reactions: the carboxylation of D-ribulose 1,5-bisphosphate, the primary event in carbon dioxide fixation, as well as the oxidative fragmentation of the pentose substrate in the photorespiration process. Both reactions occur simultaneously and in competition at the same active site.[HAMAP-Rule:MF_01338] Publication Abstract from PubMedThe slow kinetics and poor substrate specificity of the key photosynthetic CO(2)-fixing enzyme Rubisco have prompted the repeated evolution of Rubisco-containing biomolecular condensates known as pyrenoids in the majority of eukaryotic microalgae. Diatoms dominate marine photosynthesis, but the interactions underlying their pyrenoids are unknown. Here, we identify and characterize the Rubisco linker protein PYCO1 from Phaeodactylum tricornutum. PYCO1 is a tandem repeat protein containing prion-like domains that localizes to the pyrenoid. It undergoes homotypic liquid-liquid phase separation (LLPS) to form condensates that specifically partition diatom Rubisco. Saturation of PYCO1 condensates with Rubisco greatly reduces the mobility of droplet components. Cryo-electron microscopy and mutagenesis data revealed the sticker motifs required for homotypic and heterotypic phase separation. Our data indicate that the PYCO1-Rubisco network is cross-linked by PYCO1 stickers that oligomerize to bind to the small subunits lining the central solvent channel of the Rubisco holoenzyme. A second sticker motif binds to the large subunit. Pyrenoidal Rubisco condensates are highly diverse and tractable models of functional LLPS. A linker protein from a red-type pyrenoid phase separates with Rubisco via oligomerizing sticker motifs.,Oh ZG, Ang WSL, Poh CW, Lai SK, Sze SK, Li HY, Bhushan S, Wunder T, Mueller-Cajar O Proc Natl Acad Sci U S A. 2023 Jun 20;120(25):e2304833120. doi: , 10.1073/pnas.2304833120. Epub 2023 Jun 13. PMID:37311001[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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