%0 Journal Article
%T Gene encoding ¦Ã-carbonic anhydrase is cotranscribed with argC and induced in response to stationary phase and high CO2 in Azospirillum brasilense Sp7
%A Simarjot Kaur
%A Mukti N Mishra
%A Anil K Tripathi
%J BMC Microbiology
%D 2010
%I BioMed Central
%R 10.1186/1471-2180-10-184
%X One of the putative ¦Ã-CA encoding genes of A. brasilense was cloned and overexpressed in E. coli. Electrometric assays for CA activity of the whole cell extracts overexpressing recombinant GCA1 did not show CO2 hydration activity. Reverse transcription-PCR analysis indicated that gca1 in A. brasilense is co-transcribed with its upstream gene annotated as argC, which encodes a putative N-acetyl-¦Ã-glutamate-phosphate reductase. 5'-RACE also demonstrated that there was no transcription start site between argC and gca1, and the transcription start site located upstream of argC transcribed both the genes (argC-gca1). Using transcriptional fusions of argC-gca1 upstream region with promoterless lacZ, we further demonstrated that gca1 upstream region did not have any promoter and its transcription occurred from a promoter located in the argC upstream region. The transcription of argC-gca1 operon was upregulated in stationary phase and at elevated CO2 atmosphere.This study shows lack of CO2 hydration activity in a recombinant protein expressed from a gene predicted to encode a ¦Ã-carbonic anhydrase in A. brasilense although it cross reacts with anti-Cam antibody raised against a well characterized ¦Ã-CA. The organization and regulation of this gene along with the putative argC gene suggests its involvement in arginine biosynthetic pathway instead of the predicted CO2 hydration.Carbonic anhydrases (CAs, EC 4.2.1.1) are zinc metalloenzymes which catalyze the reversible hydration of carbon dioxide to bicarbonate (CO2 + H2O £¿ HCO3- + H+). This simple interconversion of a membrane-permeable gas substrate into a membrane-impermeable ionic product is vital to many important biological functions; such enzymes are thus widely distributed in nature. On the basis of differences in amino acid sequence and structure, carbonic anhydrases are divided into five distinct, evolutionarily unrelated gene families: ¦Á, ¦Â, ¦Ã and the recently discovered ¦Ä and ¦Æ [1-4]. The ¦Á-CAs are distributed in ani
%U http://www.biomedcentral.com/1471-2180/10/184