The Acetobacter xylinum gene (celB) encoding phosphoglucomutase (EC 5.4.2.2) has previously been cloned by complementation of cellulose-negative mutants. In the present report the nucleotide sequence of a 2.0 kb DNA fragment containing celB is described. Expression analysis using the bacteriophage T7 RNA polymerase promoter phi 10 resulted in identification of a probable translational start codon of celB, and this conclusion was confirmed by N-terminal amino acid sequencing of the recombinant protein. From the nucleotide sequence data it was deduced that celB encodes a protein with a calculated molecular mass of 59.6 kDa. A protein of similar size was visualized after in vitro transcription and translation, using the cloned 2.0 kb fragment as template. The results of an amino acid sequence comparison and a biochemical analysis indicated that the CelB protein is structurally and functionally related to the previously characterized human and rabbit phosphoglucomutases.