Characterization of sphingolipid long-chain base kinase in Arabidopsis thaliana

Sphingolipid long-chain base (LCB) kinase catalyses the phosphorylation of sphingolipid LCB to form LCB l-phosphate. Based on sequence identity to a m urine sphingosine kinase (murine SPHK1a), we isolated and characterized a L CB kinase-like cDNA in Arabidopsis thaliana, The deduced amino acid sequenc e of the homologous cDNA shows several regions that are highly conserved in LCB kinases from mouse, yeast, human and Caenorhabditis elegans. These reg ions are not similar to those of other known kinase families. For a functio nal identification, the homologous cDNA from A. thaliana was expressed in E scherichia coli, and LCB kinase activity was measured. The recombinant AtLc bk1 protein was found to utilize ATP and sphinganine. These results indicat e the first identification of a gene coding for a LCB kinase in plants.