 0.0) Previous knowledge hinting at the possible penton heteropentamer/double spike composition and organization is cited, but a clear account of the subject should appear in the Introduction. For instance: \"many models have been proposed\"... why? The authors should explain that the basis for these previous models is the sequence similarity between proteins P00 and P0 (see for example, Merckel et al., 0000; Huiskonen et al., 0000; Abrescia et al., 0000).  