An intracellular levansucrase gene, lscR from Rahnella aquatilis ATCC 15552, was cloned and its nucleotide sequence was determined. Nucleotide sequence analysis of this gene revealed a 1,238 bp open reading frame coding for a protein of 415 amino acids. The levansucrase was expressed by using a T7 promoter in Escherichia coli BL21 (DE3) and the enzyme activity was detected in the cytoplasmic fraction. The optimum pH and temperature of this enzyme for levan formation was pH 6 and $30^{circ}C$, respectively. The deduced amino acid sequence of the lscR gene showed a high sequence similarity (59-89%) with Gram-negative levansucrses, while the level of similarity with Gram-positive enzymes was less than 42%. Multiple alignments of levansucrase sequences reported from Gram-negative and Gram-positive bacteria revealed seven conserved regions. A comparison of the catalytic properties and deduced amino acid sequence of lscR with those of other bacterial levansucrases strongly suggest that Gram-negative and Gram-positive levansucrases have an overall different structure, but they have a similar structure at the active site.