Co-sedimentation assay for the detection of direct binding to F-actin

This protocol describes measurement of direct protein-protein interactions by actin co-sedimentation assay. The actin co-sedimentation assay is a well-established technique and has been commonly used to demonstrate binding of proteins that interact directly with actin filaments (Ahrens et al., 2012; Mehta and Sibley, 2010; Schuler et al., 2005; Singh et al., 2011). We and others have previously shown that the damaged cell-recognition molecule C-type lectin 9A (Clec9A) recognises a conserved component within nucleated and non-nucleated cells that is exposed only when the cell membrane is damaged (Srivastava and Barber, 2008; Zhang et al., 2012). Here we use Clec9A as an example and present a detailed procedure for demonstrating the direct binding of purified recombinant Clec9A ectodomain to actin filaments.