The genome of CroV has a size of 744kb and encodes for 544 predicted genes. CroV derived its name from its host, a unicellular marine zooplankton Cafeteria roenbergensis (Cro) that is the major microbial grazer in the ocean. By controlling Cro's population, CroV has a great impact on the marine ecological system. CroV is covered by a protein shell (capsid) comprised of major capsid proteins (MCP) and minor capsid proteins (mCP). The capsid not only protects the genetic material of the virus, but also helps in host-virus recognition, which is the critical initial step for viral infection. This research focuses on obtaining large amount homogenous CroV MCP for future structural studies that will facilitate the understanding of the roles of MCP in the viral life cycle.