On the basis of our two-state T7 structures and previous biochemical study of gp6.7 and gp7.3 (27) and the biochemical and structural studies of core proteins gp14, gp15, and gp16 (23, 30, 31), we propose a detailed molecular mechanism for the ejection of T7 core proteins and DNA during infection (Fig. S14). The gene discussed is CD33; the disease is infection.