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- EMDB-64722: The Chlamydomonas reinhardtii bicarbonate transporter LciA -

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Basic information

Entry
Database: EMDB / ID: EMD-64722
TitleThe Chlamydomonas reinhardtii bicarbonate transporter LciA
Map data
Sample
  • Complex: Low-CO2 inducible protein LciA
    • Protein or peptide: Low-CO2 inducible protein LCIA
KeywordsChlamydomonas reinhardtii / bicarbonate transporters / LciA / CO2-concentrating mechanism / TRANSPORT PROTEIN
Function / homologyformate transport / formate transmembrane transporter activity / Formate/nitrite transporter / Formate/nitrite transporter / Aquaporin-like / plasma membrane / Low-CO2 inducible protein LCIA
Function and homology information
Biological speciesChlamydomonas reinhardtii (plant)
Methodsingle particle reconstruction / cryo EM / Resolution: 2.37 Å
AuthorsYang Z / Guo J / Zhang P
Funding support China, 1 items
OrganizationGrant numberCountry
National Natural Science Foundation of China (NSFC)32401000 China
CitationJournal: Nat Plants / Year: 2026
Title: Structure of Chlamydomonas reinhardtii LciA guided the engineering of FNT family proteins to gain bicarbonate transport activity.
Authors: Jiaxin Guo / Zhao Yang / Xue Zhang / Feifan Liu / Miaolian Ma / Fang Yu / Jirong Huang / Peng Zhang /
Abstract: Engineering functional CO-concentrating mechanisms into C crops holds great potential for enhancing photosynthetic efficiency. Limited CO-inducible A (LciA), a chloroplast envelope bicarbonate ...Engineering functional CO-concentrating mechanisms into C crops holds great potential for enhancing photosynthetic efficiency. Limited CO-inducible A (LciA), a chloroplast envelope bicarbonate channel belonging to the formate/nitrite transporter (FNT) family, is a key algal CO2-concentrating mechanism component and has been considered as a prime candidate for introduction into C plants. However, its application has been hindered by an incomplete mechanistic understanding. Here we report the cryogenic electron microscopy structure of Chlamydomonas reinhardtii LciA. Combining structural analysis and growth assays, we determined key residues governing substrate access and permeation, and identified two substitutions (K136A/A114F) that enhance LciA activity. We found that bicarbonate selectivity is governed by electrostatic coordination mediated by Lys220 and steric constraint imposed by Ala117 and Val267 within the selectivity filter. Leveraging these insights, we successfully engineered the bacterial FNT family nitrite channel NirC through site-directed mutagenesis to gain bicarbonate transport activity, and we characterized the bicarbonate transport capacity of the Chlamydomonas nitrite channels NAR1.1/NAR1.5, which were amenable to further enhancement. Taken together, our study establishes LciA as a fundamental template for engineering and identifying FNT proteins with bicarbonate transport capability, thereby greatly expanding the molecular toolkit for synthetic biology approaches aimed at boosting photosynthetic efficiency in both algae and crops.
History
DepositionMay 19, 2025-
Header (metadata) releaseNov 26, 2025-
Map releaseNov 26, 2025-
UpdateJan 28, 2026-
Current statusJan 28, 2026Processing site: PDBc / Status: Released

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Structure visualization

Supplemental images

emd_64722.png

Downloads & links

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Map

FileDownload / File: emd_64722.map.gz / Format: CCP4 / Size: 83.7 MB / Type: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)
Projections & slices

Image control

Size
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AxesZ (Sec.)Y (Row.)X (Col.)
0.93 Å/pix.
x 280 pix.
= 260.96 Å		0.93 Å/pix.
x 280 pix.
= 260.96 Å		0.93 Å/pix.
x 280 pix.
= 260.96 Å

Surface

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Images are generated by Spider.

Voxel sizeX=Y=Z: 0.932 Å
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Histogram

Histogram (log scale)
Contour LevelBy AUTHOR: 0.7
Minimum - Maximum-2.4611795 - 4.0121603
Average (Standard dev.)-0.00087280164 (±0.11669119)
SymmetrySpace group: 1
Details

EMDB XML:

Map geometry
Axis orderXYZ
Origin000
Dimensions280280280
Spacing280280280
CellA=B=C: 260.96 Å
α=β=γ: 90.0 °

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Supplemental data

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Half map: #1

Fileemd_64722_half_map_1.map
Projections & Slices
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Half map: #2

Fileemd_64722_half_map_2.map
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Sample components

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Entire : Low-CO2 inducible protein LciA

EntireName: Low-CO2 inducible protein LciA
Components
  • Complex: Low-CO2 inducible protein LciA
    • Protein or peptide: Low-CO2 inducible protein LCIA

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Supramolecule #1: Low-CO2 inducible protein LciA

SupramoleculeName: Low-CO2 inducible protein LciA / type: complex / ID: 1 / Parent: 0 / Macromolecule list: all
Source (natural)Organism: Chlamydomonas reinhardtii (plant)

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Macromolecule #1: Low-CO2 inducible protein LCIA

MacromoleculeName: Low-CO2 inducible protein LCIA / type: protein_or_peptide / ID: 1 / Number of copies: 5 / Enantiomer: LEVO
Source (natural)Organism: Chlamydomonas reinhardtii (plant)
Molecular weightTheoretical: 32.063416 KDa
Recombinant expressionOrganism: Homo sapiens (human)
SequenceString: MVTSNGNGNG HFQAATTPVP PTPAPVAVSA PVRAVSVLTP PQVYENAINV GAYKAGLTPL ATFVQGIQAG AYIAFGAFLA ISVGGNIPG VAAANPGLAK LLFALVFPVG LSMVTNCGAE LFTGNTMMLT CALIEKKATW GQLLKNWSVS YFGNFVGSIA M VAAVVATG ...String:
MVTSNGNGNG HFQAATTPVP PTPAPVAVSA PVRAVSVLTP PQVYENAINV GAYKAGLTPL ATFVQGIQAG AYIAFGAFLA ISVGGNIPG VAAANPGLAK LLFALVFPVG LSMVTNCGAE LFTGNTMMLT CALIEKKATW GQLLKNWSVS YFGNFVGSIA M VAAVVATG CLTTNTLPVQ MATLKANLGF TEVLSRSILC NWLVCCAVWS ASAATSLPGR ILALWPCITA FVAIGLEHSV AN MFVIPLG MMLGAEVTWS QFFFNNLIPV TLGNTIAGVL MMAIAYSISF GSLGKSAKPA TAKLDYKDDD DK

UniProtKB: Low-CO2 inducible protein LCIA

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Experimental details

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Structure determination

Methodcryo EM
Processingsingle particle reconstruction
Aggregation stateparticle

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Sample preparation

Concentration27 mg/mL
BufferpH: 7.5
VitrificationCryogen name: ETHANE

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Electron microscopy

MicroscopeTFS KRIOS
Image recordingFilm or detector model: TFS FALCON 4i (4k x 4k) / Average electron dose: 50.0 e/Å2
Electron beamAcceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Electron opticsIllumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD / Nominal defocus max: 2.2 µm / Nominal defocus min: 1.2 µm
Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company

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Image processing

CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
Startup modelType of model: INSILICO MODEL
Final reconstructionResolution.type: BY AUTHOR / Resolution: 2.37 Å / Resolution method: FSC 0.143 CUT-OFF / Number images used: 169175
Initial angle assignmentType: PROJECTION MATCHING
Final angle assignmentType: PROJECTION MATCHING
FSC plot (resolution estimation)

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