Topology mapping to characterize cyanobacterial bicarbonate transporters: BicA (SulP/SLC26 family) and SbtA

Figures & data

Figure 1. Topology of the BicA-7002 bicarbonate transporter showing 14 transmembrane (TM) segments with a 7+7 inverted repeat structure. The transmembrane region shown in orange was not positively identified as crossing the membrane in the BicA mapping study (Shelden et al., 2010) but has been included based on the topology of prestin (Gorbunov et al., 2014) to provide a consensus topology for the SulP/SLC26 family. By analogy to UraA and rPRES, TM3 of BicA (shaded green) could also be partially unwound. The Saier motif refers to a 13 amino acid hydrophobic region after transmembrane helix 8 that is the second of two conserved motifs within the SulP (TC #2.53) family (Saier et al., 1999). STAS refers to the Sulphate Transporter Anti-Sigma Antagonist domain, named because of a low level of homology to a bacterial anti-sigma antagonist, SpoIIAA (Aravind & Koonin, 2000).

Figure 2. Topology of SbtA-6803 bicarbonate transporter showing 10 transmembrane segments with 5+5 inverted repeat structure based on the phoA-lacZ reporter topology study (Price et al., 2011b).

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Price GD, Shelden MC, Howitt SM. 2011b. Membrane topology of the cyanobacterial bicarbonate transporter, SbtA, and identification of potential regulatory loops. Mol Membr Biol 28:265–275

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