Abstract
Sphingoid long-chain base (LCB) kinase catalyzes the phosphorylation of LCBs to form LCB 1-phosphates. Based on sequence identity to murine sphingosine kinase (mSPHK1), we cloned and characterized the first plant LCB kinase gene from Arabidopsis (AtLCBK1). The longest AtLCBK1 cDNA isolated was 2,820 bp long, with an ORF of 2,292 bp (accession no. AB046717) that encodes a protein of 763 amino acid residues with a calculated molecular mass of 83,590 Da and a theoretical pI value of 8.3. Homology studies using the DDBJ/BLAST program revealed that the AtLCBK1 gene can be assigned to Arabidopsis chromosome 5 (AT5g23450/K19M13_8; accession no. AY139759). Using recombinant AtLCBK1 protein from Escherichia coli cells, we confirmed that the enzyme specifically phosphorylated D-erythro-dihydrosphingosine, but not N-acetyl-dihydroxysphingosine or D-threo-dihydrosphingosine. AtLCBK1 transcripts were slightly increased by low-humidity or abscisic acid treatments, suggesting that AtLCBK1 is constitutively expressed under these treatments.
