Abstract
In many pathogenic bacteria, iron starvation serves as an environmental signal that triggers the expression of virulence factors, many of which are found on the cell surface or secreted into the culture supernatant. Using the chelating agent nitrilotriacetic acid, we have established conditions for iron starvation of the important human pathogen Streptococcus pyogenes (the group A streptococcus) and determined that iron limitation results in the specific appearance of several new proteins in the culture supernatant. One of these supernatant proteins is the ADP-ribosylating protein known as streptococcal plasmin receptor (Plr) or as the streptococcal surface glyceraldehyde-3-phosphate-dehydrogenase because of its other activities. Upon iron starvation, Plr is specifically released into the culture supernatant in a time-dependent manner, and its appearance in the supernatant is not accompanied by induction of plr mRNA synthesis. Release of Plr from the bacteria may be important for the virulence of group A streptococci and the manifestation of diseases.