6KI2

The STAS domain of cyanobacteria bicarbonate transporter BicA

Summary for 6KI2

• Entry DOI: 10.2210/pdb6ki2/pdb
• Descriptor: Low affinity sulfate transporter, SULFATE ION (3 entities in total)
• Functional Keywords: bicarbonate transporter, co2-concentrating mechanisms (ccm), cyanobacteria, solute carrier (slc), stas domain, transport protein
• Biological source: Synechocystis sp. PCC 6803
• Total number of polymer chains: 2
• Total formula weight: 35511.12

Authors

Zhang, P.,Wang, C.C. (deposition date: 2019-07-17, release date: 2019-11-20, Last modification date: 2024-10-30)

Primary citation

Wang, C.,Sun, B.,Zhang, X.,Huang, X.,Zhang, M.,Guo, H.,Chen, X.,Huang, F.,Chen, T.,Mi, H.,Yu, F.,Liu, L.N.,Zhang, P.
Structural mechanism of the active bicarbonate transporter from cyanobacteria.
Nat.Plants, 5:1184-1193, 2019

PubMed Abstract: Bicarbonate transporters play essential roles in pH homeostasis in mammals and photosynthesis in aquatic photoautotrophs. A number of bicarbonate transporters have been characterized, among which is BicA-a low-affinity, high-flux SLC26-family bicarbonate transporter involved in cyanobacterial CO-concentrating mechanisms (CCMs) that accumulate CO and improve photosynthetic carbon fixation. Here, we report the three-dimensional structure of BicA from Synechocystis sp. PCC6803. Crystal structures of the transmembrane domain (BicA) and the cytoplasmic STAS domain (BicA) of BicA were solved. BicA was captured in an inward-facing HCO-bound conformation and adopts a '7+7' fold monomer. HCO binds to a cytoplasm-facing hydrophilic pocket within the membrane. BicA is assembled as a compact homodimer structure and is required for the dimerization of BicA. The dimeric structure of BicA was further analysed using cryo-electron microscopy and physiological analysis of the full-length BicA, and may represent the physiological unit of SLC26-family transporters. Comparing the BicA structure with the outward-facing transmembrane domain structures of other bicarbonate transporters suggests an elevator transport mechanism that is applicable to the SLC26/4 family of sodium-dependent bicarbonate transporters. This study advances our knowledge of the structures and functions of cyanobacterial bicarbonate transporters, and will inform strategies for bioengineering functional BicA in heterologous organisms to increase assimilation of CO.

PubMed: 31712753
DOI: 10.1038/s41477-019-0538-1

Experimental method

X-RAY DIFFRACTION (2.197 Å)