Tropomodulin on An Actin Filament (IMAGE) University of Pennsylvania School of Medicine Caption This is a representation of the atomic structure of tropomodulin at the minus end of the actin filament in muscle sarcomeres. Tropomodulin interacts with the first three actin subunits of the filament. The regions of tropomodulin that interact with actin are colored magenta, and the three actin subunits involved in this interaction are represented by two shades of blue, and purple for the interacting surface of the third subunit. Other subunits of the filament are colored gray. The actin filament also has two tropomyosin coiled coils bound symmetrically on each side (orange). At the minus end, tropomodulin also interacts with the tropomyosin coiled coils, and the region responsible for this interaction is colored green. Credit Yadaiah Madasu, Ph.D., Perelman School of Medicine at the University of Pennsylvania, Science Usage Restrictions None License Licensed content 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.