BicA and related proteins of the SulP family diverged from a common ancestor with archaeal NCS-2 proteins

AbstractBicA is a cyanobacterial bicarbonate transporter that belongs to the widespread Sulfate Permease (SulP) family of proteins. To understand the evolutionary trajectory of BicA, its distant homologs were identified by using the Position-Specific Iterative Basic Local Alignment Search Tool (PSI BLAST) against all organisms excluding cyanobacteria and manually screened to include homologs performing different functions. A total of 43 proteins were short-listed for the phylogenetic tree construction and conserved domain analysis. The results show a distant homology between BicA and archaeal proteins of the Nucleobase Cation Symporter (NCS-2) family. The archaeal NCS-2 family members dominate in the lower clades of the phylogenetic tree, while the upper clades consist mostly of bacterial sulphate and anion transporters of the SulP family. Analysis of BicA for conserved domains shows pbuX, UraA and AzgA domains in common with NCS-2 family proteins, which supports their homologous relationship. We propose that cyanobacterial BicA and related proteins of the SulP family potentially diverged from or shared a common ancestor with archaeal NCS-2 proteins.