Gene Ontology annotation through association of InterPro records with GO terms
A gene family of silicon transporters.
Analysis of Thalassiosira pseudonana silicon transporters indicates distinct regulatory levels and transport activity through the cell cycle.
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TpSIT1 and TpSIT2 are 88% identical; transcript and protein levels are uncoupled through the cell cycle.
"Pairwise comparison between each SIT revealed 88% amino acid identity and 95% similarity between TpSIT1 and TpSIT2."
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Published TpSIT1 numbering (antigen at residues 318-332) is on the 517-residue cDNA sequence, not the 464-residue gene model.
"The sequence of a 15-residue region corresponding to amino acids 318 to 332 of TpSIT1 (sequence PANERGTSFFGRKTC)"
Silicon uptake in diatoms revisited: a model for saturable and nonsaturable uptake kinetics and the role of silicon transporters.
Expression, purification, and reconstitution of a diatom silicon transporter.
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A purified T. pseudonana SIT (identified as TpSIT3 in PMID:27305972) transports silicic acid in proteoliposomes dependent on a sodium gradient.
"silicon uptake was found to be dependent upon an applied sodium gradient"
Evidence for a regulatory role of diatom silicon transporters in cellular silicon responses.
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eGFP-tagged SIT1 and SIT2 localize to the plasma membrane.
"Here we demonstrated that eGFP-tagged SIT1 and SIT2 were indeed localized in the plasma membrane"
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Joint SIT1/SIT2 knockdown slows silicic acid depletion at 20 uM but not at 200 uM.
"the wild type depleted the medium of silicon by 2 h, whereas the transgenic clones lagged and took 1 h longer"
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A silicic-acid sensing role is proposed as a hypothesis.
"Their primary role is to sense silicic acid levels to evaluate whether the cell can proceed with its cell wall formation and division processes."
Direct evidence of the molecular basis for biological silicon transport.
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Purified PtSIT1 and NaSIT transport silicic acid in proteoliposomes with Michaelis-Menten kinetics, driven by a sodium gradient; TpSIT1 expressed poorly in yeast and was not assayed.
"TpSIT1 and ToSIT were expressed at very low levels"
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The eleven full-length SITs synthesized, TpSIT1 among them, were all 506-599 residues long, longer than the 464-residue B8C2V9 gene model.
"All of these protein sequences were between 506 and 599 amino acids in length."
Computational modelling of diatom silicic acid transporters predicts a conserved fold with implications for their function and evolution.
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AlphaFold models of SITs share a common membrane fold with a central polar substrate site, consistent with alternating access.
"Substrate docking reveals how conserved polar residues could interact with silicic acid at a central solvent-accessible binding site, consistent with an alternating access mechanism of transport."
UniProt TrEMBL entry B8C2V9
SIT1/SIT2 gene-model comparison with cDNA-derived entries
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B8C2V9 lacks the first 53 residues of the cloned TpSIT1 (Q0QVM8), including a probable N-terminal transmembrane segment.
"N-terminal residues absent from B8C2V9: 53"