CHARACTERIZATION OF THE PASTEURELLA-MULTOCIDA SKP AND FIRA GENES

A 2.9-kb fragment of the Pasteurella multocida (Pm) genome encoding pr oteins p25 (25 kDa) and p28 (28 kDa) has previously been cloned and ex pressed in Escherichia coli (Ec). In the present paper, the nucleotide (nt) sequence of a 1.8-kb subfragment encoding the two proteins is de scribed, The cloned fragment contains three open reading frames (ORFs) . ORF1 is incomplete. ORF2 is homologous to the skp gene of Ec. ORF3 o verlaps ORF2 and is highly homologous to the fir A gene of Ec. The skp and fir A genes are part of an operon governing the first steps of li pid A synthesis. Comparing the nt sequence with the N-terminal sequenc es of p25 and p28 revealed that the two proteins are encoded by ORF2 ( skp). The preprotein p28 is converted into p25 by cleavage of a 23-ami no-acid leader peptide. Though it serologically cross-reacts with pori n H of Pm, p25 is not related to known bacterial porins.