Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 6/3/1996
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Carbamoyl phosphate synthase (CPS, E.C. 22.214.171.124) catalyzes formation of carbamoyl phosphate, a precursor in the synthesis of citrulline. Citrulline, being part of arginine metabolism, is produced in high amounts in Alnus root nodules and functions as a transport form of nitrogen to the shoot. A partial cDNA from Alnus glutinosa with sequence homology to the small subunit of CPS encoded by carA in bacteria, was used to isolate a full-length 1.7 kb cDNA from an Alnus incana root nodule cDNA library. Sequence analysis revealed highest amino acid sequence similarity to bacterial small subunit CPSs followed by fungal CPSs. A motif similar to a glutamine amidotransferase class I active site was detected. This is consistent with the role of the small subunit in other organisms as a glutaminase providing the ammonia used by the large subunit for carbamoyl phosphate synthesis. In addition, sequence motifs of a putative transitpeptide for mitochondrial import was found at the amino terminus. Expression of CPS mRNA was greatly enhanced in root nodules and low to nondetectable in other organs.