PubMed:10557362
Annnotations
{"target":"https://pubannotation.org/docs/sourcedb/PubMed/sourceid/10557362","sourcedb":"PubMed","sourceid":"10557362","source_url":"http://www.ncbi.nlm.nih.gov/pubmed/10557362","text":"Identification of an ATP-binding cassette transporter involved in bicarbonate uptake in the cyanobacterium Synechococcus sp. strain PCC 7942.\nExposure of cells of cyanobacteria (blue-green algae) grown under high-CO(2) conditions to inorganic C-limitation induces transcription of particular genes and expression of high-affinity CO(2) and HCO(3)(-) transport systems. Among the low-CO(2)-inducible transcription units of Synechococcus sp. strain PCC 7942 is the cmpABCD operon, encoding an ATP-binding cassette transporter similar to the nitrate/nitrite transporter of the same cyanobacterium. A nitrogen-regulated promoter was used to selectively induce expression of the cmpABCD genes by growth of transgenic cells on nitrate under high CO(2) conditions. Measurements of the initial rate of HCO(3)(-) uptake after onset of light, and of the steady-state rate of HCO(3)(-) uptake in the light, showed that the controlled induction of the cmp genes resulted in selective expression of high-affinity HCO(3)(-) transport activity. The forced expression of cmpABCD did not significantly increase the CO(2) uptake capabilities of the cells. These findings demonstrated that the cmpABCD genes encode a high-affinity HCO(3)(-) transporter. A deletion mutant of cmpAB (M42) retained low CO(2)-inducible activity of HCO(3)(-) transport, indicating the occurrence of HCO(3)(-) transporter(s) distinct from the one encoded by cmpABCD. HCO(3)(-) uptake by low-CO(2)-induced M42 cells showed lower affinity for external HCO(3)(-) than for wild-type cells under the same conditions, showing that the HCO(3)(-) transporter encoded by cmpABCD has the highest affinity for HCO(3)(-) among the HCO(3)(-) transporters present in the cyanobacterium. This appears to be the first unambiguous identification and description of a primary active HCO(3)(-) transporter.","tracks":[{"project":"PMID_GLOBAL","denotations":[{"id":"T1","span":{"begin":132,"end":135},"obj":"DiseaseOrPhenotypicFeature"},{"id":"T3","span":{"begin":447,"end":450},"obj":"DiseaseOrPhenotypicFeature"}],"attributes":[{"id":"A1","pred":"mondo_id","subj":"T1","obj":"0004974"},{"id":"A2","pred":"mondo_id","subj":"T1","obj":"0022673"},{"id":"A3","pred":"mondo_id","subj":"T3","obj":"0004974"},{"id":"A4","pred":"mondo_id","subj":"T3","obj":"0022673"},{"subj":"T1","pred":"source","obj":"PMID_GLOBAL"},{"subj":"T3","pred":"source","obj":"PMID_GLOBAL"}]}],"config":{"attribute types":[{"pred":"source","value type":"selection","values":[{"id":"PMID_GLOBAL","color":"#9397ec","default":true}]}]}}