NEW OUTER MEMBRANE-ASSOCIATED PROTEASE OF ESCHERICHIA-COLI K-12

The gene for a new outer membrane-associated protease, designated OmpP , of Escherichia coli has been cloned and sequenced. The gene encodes a 315-residue precursor protein possessing a 23-residue signal sequenc e. Including conservative substitutions and omitting the signal peptid es, OmpP is 87% identical to the outer membrane protease OmpT. OmpP po ssessed the same enzymatic activity as OmpT. Immuno-electron microscop y demonstrated the exposure of the protein at the cell surface. Digest ion of intact cells with proteinase K removed 155 N-terminal residues of OmpP, while the C-terminal half remained protected. It is possible that much of this N-terminal part is cell surface exposed and carries the enzymatic activity. Synthesis of OmpP was found to be thermoregula ted, as is the expression of ompT (i.e., there is a low rate of synthe sis at low temperatures) and, in addition, was found to be controlled by the cyclic AMP system.