CLONING AND SEQUENCING OF 2 GENES, PRTA AND PRTB, FROM MYXOCOCCUS-XANTHUS, ENCODING PRTA AND PRTB PROTEASES, BOTH OF WHICH ARE REQUIRED FORTHE PROTEASE ACTIVITY

The sequence of a 1955-bp TaqI DNA fragment from Myxococcus xanthus wa s determined. This fragment contains two complete genes, designated pr tA and prtB. The prtA and prtB ORFs extend over 828 and 798 bp, respec tively. They are separated only by 3 nt and appear to be present in a polycistronic transcriptional unit. A typical lipoprotein signal seque nce is present at the N terminus of the two deduced polypeptides. The aa sequence of PrtA shows a high degree of identity to the region adja cent to the Ser residue belonging to the catalytic triad of serine pro teases from Staphylococcus aureus and Enterococcus faecalis. It also e xhibits features characteristic of trypsin-like serine proteases in th at it contains the same pattern of variable and conserved regions. The deduced aa sequence of PrtB reveals a signature zinc-binding consensu s motif (HEXXHXXGXXH/Met-turn) characteristic of the class of metallop roteases called metzincins. Plasmids containing prtA, prtB, or both we re constructed. Protease activity studies of Escherichia coli clones c ontaining these plasmids showed that both genes are necessary for this activity, whatever their cis or trans position. As prtB produces a pu tative membrane-bound lipoprotein of 266 aa, the protease activation m ust occur at the membrane level. (C) 1997 Elsevier Science B.V.