STRUCTURAL AND FUNCTIONAL-RELATIONSHIPS BETWEEN PASTEURELLA-MULTOCIDA AND ENTEROBACTERIAL ADENYLATE CYCLASES

The Pasteurella multocida adenylate cyclase gene has been cloned and expressed in Escherichia coli. The primary structure of the protein (838 amino acids) deduced from the corresponding nucleotide sequence was compared with that of E. coli. The two enzymes have similar molecular sizes and, based on sequence conservation at the protein level, are likely to be organized in two functional domains: the amino-terminal catalytic domain and the carboxy-terminal regulatory domain. It was shown that P. multocida adenylate cyclase synthesizes increased levels of cyclic AMP in E. coli strains deficient in the catabolite gene activator protein compared with wild-type strains. This increase does not occur in strains deficient in both the catabolite gene activator protein and enzyme III-glucose, indicating that a protein similar to E. coli enzyme III-glucose is involved in the regulation of P. multocida adenylate cyclase. It also indicates that the underlying process leading to enterobacterial adenylate cyclase activation has been conserved through evolution.