title: Identification of a SulP-type bicarbonate transporter in marine cyanobacteria.
abstract: Cyanobacteria possess a highly effective CO(2)-concentrating mechanism that elevates CO(2) concentrations around the primary carboxylase, Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase). This CO(2)-concentrating mechanism incorporates light-dependent, active uptake systems for CO(2) and HCO(-)(3). Through mutant studies in a coastal marine cyanobacterium, Synechococcus sp. strain PCC7002, we identified bicA as a gene that encodes a class of HCO(-)(3) transporter with relatively low transport affinity, but high flux rate. BicA is widely represented in genomes of oceanic cyanobacteria and belongs to a large family of eukaryotic and prokaryotic transporters presently annotated as sulfate transporters or permeases in many bacteria (SulP family). Further gain-of-function experiments in the freshwater cyanobacterium Synechococcus PCC7942 revealed that bicA expression alone is sufficient to confer a Na(+)-dependent, HCO(3)(-) uptake activity. We identified and characterized three cyanobacterial BicA transporters in this manner, including one from the ecologically important oceanic strain, Synechococcus WH8102. This study presents functional data concerning prokaryotic members of the SulP transporter family and represents a previously uncharacterized transport function for the family. The discovery of BicA has significant implications for understanding the important contribution of oceanic strains of cyanobacteria to global CO(2) sequestration processes.
authors.affiliation: Molecular Plant Physiology Group, Research School of Biological Sciences, Science Faculty, Australian National University, P.O. Box 475, Canberra ACT 0200, Australia. dean.price@anu.edu.au
authors.forename: G Dean
authors.initials: GD
authors.lastname: Price
authors.forename: Fiona J
authors.initials: FJ
authors.lastname: Woodger
authors.forename: Murray R
authors.initials: MR
authors.lastname: Badger
authors.forename: Susan M
authors.initials: SM
authors.lastname: Howitt
authors.forename: Loraine
authors.initials: L
authors.lastname: Tucker
mesh_terms: D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport; D002244:Carbon / Q000737:chemistry / Q000494:pharmacology; D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism; D000458:Cyanobacteria / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005822:Genetic Vectors; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009154:Mutation; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis; D010802:Phylogeny; D010827:Physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012273:Ribulose-Bisphosphate Carboxylase / Q000494:pharmacology; D012825:Silicon / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D027982:Sodium-Bicarbonate Symporters / Q000737:chemistry* / Q000502:physiology; D046940:Synechococcus / Q000378:metabolism
chemical_list: D001639:Bicarbonates; D027982:Sodium-Bicarbonate Symporters; D002245:Carbon Dioxide; D002244:Carbon; D012964:Sodium; D012273:Ribulose-Bisphosphate Carboxylase; D010100:Oxygen; D012825:Silicon