Electronic Gene Ontology annotations created by transferring manual GO annotations between related proteins based on shared sequence features
Combined Automated Annotation using Multiple IEA Methods
Sequence, evolution and differential expression of the two genes encoding variant small subunits of ribulose bisphosphate carboxylase/oxygenase in Chlamydomonas reinhardtii.
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Chlamydomonas has two expressed small-subunit genes (RBCS1, RBCS2) encoding variants that differ by four residues.
"The two genes encode variant small subunits that differ by four amino acid residues. Both genes are expressed"
Elimination of the Chlamydomonas gene family that encodes the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase.
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A deletion of both RBCS genes is photosynthesis-deficient and is complemented by either RBCS1 or RBCS2, so either small subunit is sufficient for holoenzyme assembly and function.
"Thus, either small subunit is sufficient for holoenzyme assembly and function."
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Without small subunits, translation of the chloroplast-encoded large subunit is inhibited.
"In the absence of small subunits, expression of chloroplast-encoded large subunits appears to be inhibited at the level of translation."
First crystal structure of Rubisco from a green alga, Chlamydomonas reinhardtii.
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The 1.4 A crystal structure shows Chlamydomonas Rubisco is an L8S8 holoenzyme; the SSU betaA-betaB loop is longer than in spinach and affects holoenzyme stability and catalysis.
"Overall, the structure shows high similarity to the previously determined structures of L8S8 Rubisco enzymes."
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Post-translational modifications include N-terminal methylation.
"These include cysteine and N-terminal methylations and proline 4-hydroxylations."
Functional hybrid rubisco enzymes with plant small subunits and algal large subunits: engineered rbcS cDNA for expression in chlamydomonas.
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The active site is in the large subunit; small subunits influence carboxylation efficiency and CO2/O2 specificity.
"Although the large subunit contains the active site, a family of rbcS nuclear genes encodes the Rubisco small subunits, which can also influence the carboxylation catalytic efficiency and CO(2)/O(2) specificity of the enzyme."
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Hybrid enzymes with plant SSUs are catalytically proficient but the strains lack pyrenoids, pointing to the SSU as the pyrenoid targeting determinant.
"It appears that small subunits contain the structural elements responsible for targeting Rubisco to the algal pyrenoid"
Rubisco small-subunit α-helices control pyrenoid formation in Chlamydomonas.
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Pyrenoid formation, Rubisco aggregation and CCM activity depend on the two surface-exposed SSU alpha-helices.
"pyrenoid occurrence was shown to be conditioned by the amino acid composition of two surface-exposed α-helices of the SSU: higher plant-like helices knock out the pyrenoid, whereas native algal helices establish a pyrenoid."
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Introducing spinach helices into the native Chlamydomonas RBCS1 (reciprocal mutant) abolishes the pyrenoid.
"Proof that both Chlamydomonas SSU α-helices are an absolute requirement for pyrenoid integrity was shown by the reciprocal mutant: the pyrenoid was lost when both spinach SSU α-helices were introduced into an otherwise Chlamydomonas wild-type LSU+SSU holoenzyme"
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The reciprocal construct was built on native RBCS1.
"The reverse construct (substituting the algal helices with the spinach helices) was undertaken on a vector that contained the native Chlamydomonas RbcS1 , flanked by the same regulatory sequences as above."
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In pyrenoid-negative lines Rubisco is dispersed through the stroma.
"In contrast, immunolocalization of Rubisco in the pyrenoid-negative lines (spinach hybrid and reciprocal) showed Rubisco was redistributed throughout the stroma, similar to higher plant chloroplasts."
The structural basis of Rubisco phase separation in the pyrenoid.
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Each Rubisco holoenzyme has eight EPYC1 binding sites, one on each small subunit; interface mutations disrupt binding, phase separation and pyrenoid formation.
"indicates that each Rubisco holoenzyme has eight binding sites for EPYC1, one on each Rubisco small subunit. Interface mutations disrupt binding, phase separation and pyrenoid formation."
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EPYC1 residues form salt bridges with D23 and E24 of SSU helix A and with R91 of helix B.
"EPYC1 residues R64 and R71 interact with E24 and D23, respectively, of Rubisco small subunit α-helix A, and EPYC1 residue E66 interacts with R91 of Rubisco small subunit α-helix B."
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RBCS1 point mutants D23A/E24A and M87D/V94D were built in the native RBCS1 gene and expressed in the rbcS deletion strain.
"which encode RBCS1D23A/E24A, and RBCS1M87D/V94D, respectively."
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The mutants lack a visible pyrenoid matrix and grow poorly under conditions requiring the pyrenoid.
"Rubisco small subunit mutations D23A/E24A or M87D/V94D caused a growth defect under conditions requiring a functional pyrenoid"
A repeat protein links Rubisco to form the eukaryotic carbon-concentrating organelle.
The Eukaryotic CO(2)-Concentrating Organelle Is Liquid-like and Exhibits Dynamic Reorganization.
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RbcS1-Venus marks the pyrenoid matrix and partly disperses into the stroma during pyrenoid division.
"A portion of the RbcS1-Venus and EPYC1-Venus signals rapidly dispersed from the pyrenoid matrix into the stroma for ~20 minutes near the end of chloroplast and pyrenoid division"
The phase separation underlying the pyrenoid-based microalgal Rubisco supercharger.
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Purified Rubisco and EPYC1 are necessary and sufficient to form liquid droplets, and phase-separated Rubisco remains active.
"two proteins, Rubisco and the linker protein Essential Pyrenoid Component 1 (EPYC1), are both necessary and sufficient to phase separate and form liquid droplets. The phase-separated Rubisco is functional."
The pyrenoidal linker protein EPYC1 phase separates with hybrid Arabidopsis-Chlamydomonas Rubisco through interactions with the algal Rubisco small subunit.
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EPYC1 binds the Chlamydomonas SSU, dependent on its two surface-exposed helices; a Chlamydomonas SSU lets hybrid Arabidopsis Rubisco phase separate with EPYC1.
"Interaction is crucially dependent on the two surface-exposed α-helices of the Chlamydomonas SSU."
Evolution of rubisco complex small subunit transit peptides from algae to plants.