In the figure 4 legend, the sentence: “The structure of DPC is above the panel.” should be replaced by “The structure of DPC is inset into the panel, and the secondary structure is shown above the panel.” Also, in the figure 5 legend, “The conservation of structurally and functionally important PX domain residues are shown ...” should be replaced by “The conservation of structurally and functionally important PX domain residues is shown ...”

This PDF posted on 4 June 2001 replaces the one originally posted on 24 May 2001. The corrected version of this paper will appear in the July issue of the journal.