PMID:31391312

Thylakoid localized bestrophin-like proteins are essential for the CO(2) concentrating mechanism of Chlamydomonas reinhardtii.

BST2 is Cre16.g663400, one of three paralogous bestrophin-like genes clustered on chromosome 16

"BST1 (Cre16.g662600), BST2 (Cre16.g663400), and BST3 (Cre16.g663450) (collectively BST1–3) are paralogous bestrophin-like genes"
BST1-3 are >80% identical; BST2 and BST3 were earlier called LCI11

"BST2 and BST3 were previously reported as LCI11 by Fang et al. (16). An alignment between the 3 Chlamydomonas bestrophin-like proteins showed that the proteins are >80% identical to one another"
BST1-3 are predicted chloroplast membrane proteins with a transit peptide

"predicted that each BST protein had a chloroplast transit peptide and was likely to be a chloroplast membrane protein"
Homology modelling supports a pentameric bestrophin fold and an anion-selective pore

"the selective pore is positively charged, supporting the hypothesis that BST1–3 transport negatively charged ions"
BST2 is induced in ambient CO2, with reduced induction in the cia5 mutant

"BST2 transcript levels in cia5 cells showed reduced induction in ambient CO2 when compared with D66 cells, where BST2 transcript levels increase in ambient CO2 conditions."
BST2 is expressed more highly than BST1

"BST1 had a lower level of expression than BST2 or BST3"
Venus-tagged BST1-3 (including BST2) localize to the chloroplast thylakoid membranes, enriched at the pyrenoid periphery

"The localization studies visually showed that BST1, BST2, and BST3 were preferentially concentrated near the pyrenoid"
BST1-3 are functionally redundant; single bst3 has a weak phenotype

"This led us to think that BST1 or BST2 function might be redundant with BST3"
Triple knockdown (including BST2 transcript) impairs low-CO2 growth and Ci uptake

"RT-qPCR showed that bsti-1 had significantly reduced expression of BST1, BST2, and BST3 compared with D66"
BST1-3 are proposed (not shown) to deliver HCO3- to lumenal CAH3

"We propose that BST1–3 are the transporters that bring HCO3− to CAH3 inside the thylakoid."
BST1-3 function differs from Arabidopsis VCCN1 (opposite pmf effect)

"The presence of AtVCCN1 decreases pmf in Arabidopsis, but the presence of the 3 BST proteins increases pmf in Chlamydomonas."

PMID:28938113

A Spatial Interactome Reveals the Protein Organization of the Algal CO(2)-Concentrating Mechanism.

Cre16.g663400 (BST2) was recovered as an interactor of both the BST1 (Cre16.g662600) and BST3 (LCI11, Cre16.g663450) baits

"LCI11 and Cre16.g662600 directly interact, and both also interact with another bestrophin-like protein, Cre16.g663400."
The LCIB/LCIC interactions were reported for BST3 and BST1, not for BST2

"Both LCIB and LCIC interact with LCI11 (Cre16.g663450), and LCIC also interacts with Cre16.g662600"

PMID:39240724

Bestrophin-like protein 4 is involved in photosynthetic acclimation to light fluctuations in Chlamydomonas.

BST1-3 are the model's thylakoid HCO3- channels, distinct from the pyrenoid-tubule BST4

"In the current model, bicarbonate (HCO3−) is channeled into the thylakoid lumen by bestrophin-like proteins 1-3 (BST1-3)"
BST1-3 are distributed throughout the thylakoid and enriched at the pyrenoid periphery

"While BST1-3 localizes throughout the thylakoid membrane and is enriched at the pyrenoid periphery"
HCO3- channel activity for BST-family proteins remains a hypothesis

"BST4 may function as an HCO3− channel, like that proposed for BST1-3 (Mukherjee et al. 2019), but there are currently no data to support this hypothesis"

PMID:27216227

A voltage-dependent chloride channel fine-tunes photosynthesis in plants.

Arabidopsis VCCN1 (AT3G61320; PAINT donor for the IBA rows) is a voltage-dependent thylakoid Cl- channel shown by planar bilayer electrophysiology

"In this study, we bring evidence that AtVCCN1 forms a voltage-dependent Cl− channel, is located in the thylakoid membrane"

PMID:38478576

Low-CO2-inducible bestrophins outside the pyrenoid sustain high photosynthetic efficacy in diatoms.

In the diatom Phaeodactylum, knockout of the low-CO2-induced thylakoid bestrophin PtBST1 nearly abolishes the inducible CCM

"However, the striking phenotype of ΔPtBST1 mutants, which almost lacks in the LC-inducible CCM, clearly indicates that even the BST factors outside of the pyrenoid are vital components of the CO2-evolving machinery"

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

GO_REF:0000108

Automatic assignment of GO terms using logical inference, based on on inter-ontology links