IRON STARVATION CAUSES RELEASE FROM THE GROUP-A STREPTOCOCCUS OF THE ADP-RIBOSYLATING PROTEIN CALLED PLASMIN RECEPTOR OR SURFACE GLYCERALDEHYDE-3-PHOSPHATE-DEHYDROGENASE

In many pathogenic bacteria, iron starvation serves as an environmenta l signal that triggers the expression of virulence factors, many of wh ich are found on the cell surface or secreted into the culture superna tant. Using the chelating agent nitrilotriacetic acid, we have establi shed conditions for iron starvation of the important human pathogen St reptococcus pyogenes (the group A streptococcus) and determined that i ron limitation results in the specific appearance of several new prote ins in the culture supernatant. One of these supernatant proteins is t he ADP-ribosylating protein known as streptococcal plasmin receptor (P lr) or as the streptococcal surface glyceraldehyde-3-phosphate-dehydro genase because of its other activities. Upon iron starvation, Plr is s pecifically released into the culture supernatant in a time-dependent manner, and its appearance in the supernatant is not accompanied by in duction of plr mRNA synthesis. Release of Plr from the bacteria may be important for the virulence of group A streptococci and the manifesta tion of diseases.