This video illustrates the common Cas9 functional core defined by structural comparison of SpyCas9 and AnaCas9. Surface representations of SpyCas9 (top) and AnaCas9 (bottom) with conserved RuvC, HNH, Arg-rich, Topo-homology and CTD domains, are colored as in Fig. 3F. The structurally preserved portion of the alpha-helical lobe is colored green. The non-conserved regions of each protein are colored in gray (see also Figure 3F). This video relates to a paper that appeared in the Feb. 6, 2014, issue of Science Express, published by AAAS. The paper, by Martin Jinek and at the University of Zurich in Zurich, Switzerland, and colleagues was titled, "Structures of Cas9 Endonucleases Reveal RNA-Mediated Conformational Activation."