A NEW EXTRACELLULAR PROTEIN OF PSEUDOMONAS-AERUGINOSA PA103 REGULATEDBY REGA

The expression of exotoxin A (ExoA) from Pseudomonas aeruginosa is inf luenced by iron and is under the control of the regulatory gene regA. To test whether regA plays a role in the expression of other iron-regu lated proteins a RegA(-) mutant was constructed by insertional mutagen esis. The polypeptide pattern of this mutant (PA103R) was compared wit h the parental strain (PA103) and a trans-complemented strain PA103R(p REX18) after growth of the strains in conditions containing low or hig h concentrations of iron. An iron-regulated 42 kDa protein (RRP) was i dentified and purified from the culture supernatant of PA103 and PA103 R(pREX18) which was missing in PA103R. Database analysis of the N-term inal sequence of this regA-regulated protein (RRP) revealed no similar ity to other proteins. Preliminary investigations into the function of RRP revealed that it has no proteolytic or cytotoxic activity. Using two-dimensional electrophoretic analysis of whole cells, a technique w hich allowed separation of over 600 polypeptides, we were unable to id entify any other iron-regulated protein whose expression was regulated by regA.