image: This image shows the proposed binding site of the PAD4-activating antibody. The PAD4 enzyme is composed of two pieces (light gray and dark gray) that are connected in the middle. This connection point between the two halves is important for binding to calcium (blue spheres) and interacting with proteins that will be modified by the PAD4 enzyme. The newly discovered PAD4-activating antibody seems to bind in this region (shown in yellow and purple) and substitutes for some of the calcium that is usually required to modify proteins. This allows the enzyme to work with the small amounts of calcium normally present in the body. This image relates to a paper that appeared in the May 22, 2013, issue of Science Translational Medicine, published by AAAS. The paper, by Dr. E. Darrah at The Johns Hopkins University, School of Medicine in Baltimore, Md., and colleagues was titled, "Erosive Rheumatoid Arthritis Is Associated with Antibodies That Activate PAD4 by Increasing Calcium Sensitivity." view more
Credit: Image courtesy of <i>Science Translational Medicine</i>/AAAS