Cloning and sequencing of a Clostridium perfringens sialidase gene

Escherichia coli was transformed with pUC vectors containing Sau3A restriction fragments (RF) of Clostridium perfringens DNA. Two clones expressed sialidase activity when assayed with the fluorogenic substrate 4-methylumbelliferyl-alpha-D-N-acetylneuraminic acid. A synthetic oligonucleotide representing the N-terminus of the expressed enzyme hybridized with the clostridial insert and with a corresponding 2.1 kb Sau3A RF of the C. perfringens genome. The insert reduced to 1.4 kb, which still encoded active sialidase, has been sequenced. The structural gene encodes 382 amino acids representing an Mr of 42770. A hydrophobic leader sequence is absent. Upstream from the initiation codon ATG, a GA-rich region is found and considered as the Shine-Dalgarno sequence. Homology with the N-terminus of the Vibrio cholerae sialidase gene and with viral sialidase sequences was not found.