A full-length cDNA encoding Neurospora crassa calmodulin was isolated from λZAP II cDNA expression library. The open reading frame encodes a protein of 148 amino acid residues with a calculated Mr, of 16,865 Da. Using site-directed mutagenesis, the complete cDNA was ligated into a trc promoter-regulated bacterial expression vector to allow expression of N. crassa calmodulin in E. coli. The expressed protein was found to be identical to the native protein on the basis of some of its biochemical properties. Finally, Southern analysis of restriction digests of genomic DNA indicates that calmodulin is encoded by a single-copy gene.