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The Science Seminar Series: February 14, 2008 4pm
Shr, a Multifunctional Protein in Group A Streptococcus that is NEAT
Dr. Zehava Eichenbaum
Georgia State University, Biology Department
Powell HallTime: 4:00 - 5:00pm
Abstract
The Streptococcal hemoprotein receptor (Shr) is an exported protein in Group A Streptococcus (GAS) which binds to hemoglobin, myoglobin, and hemoglobin-heptoglobin complex. In this study, we explored Shr’s function and contribution to GAS pathogenesis. We previously reported that Shr is found in association with whole cells and in the culture supernatant. Here we demonstrate that cell-associated Shr could not be released from the bacteria by the muralytic enzyme mutanolysin, and instead was localized to the insoluble fraction. Shr, however, was available on GAS exterior, exposed to the extracellular environment. Two NEAT (NEAr Transporter) domains are found in Shr; NEAT is implicatedin binding to heme, hemoproteins, and in some cases to ECM constituents. Purified Shr specifically interacted with the immobilized fibronectin and laminin. GAS infection elicited a high titer of Shr antibodies in mice, demonstrating that it is expressed in vivo. Shr inactivation resulted in 50% reduction of bacterial attachment to human epithelial cells and attenuated virulence in an intramuscular zebrafish model system. In summary, Shr is a broad-spectrum receptor that in addition to its role in heme acquisition, functions as an adhesin. The contribution of this multifunctional protein to the infection process of GAS is discussed.