Model of Action of the MMP-activated Anthrax Toxin (image) American Society for Biochemistry and Molecular Biology Share Print E-Mail Caption After binding to cell surface markers, the MMP-activated PA protein (PA-L1) is cleaved by surface associated MMPs, releasing the PA20 fragment. The remaining receptor-bound fragment rapidly oligomerizes to form a heptamer. Up to three molecules of anthrax lethal factor (LF) bind to the heptamer, which is then internalized. Once inside the cell, the complex encounters an acidic environment, which induces a conformational change and allows the LF to enter the cytosol. LF released into the cytosol shuts down multiple signaling pathways, leading to inhibition of tumor angiogenesis and human melanoma cell death. Credit The image was created by Drs. Shihui Liu, Mahtab Moayeri, and Stephen H. Leppla. Usage Restrictions none Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.