Nature 380, 456–460 (1996)

In the legend to Fig. 3, lines 11 and 12 should read: “Arg 232 (NH1) makes two hydrogen bonds with G9(06) and G9(N7).” In panel b, a dashed line indicating a hydrogen bond to base A10 should be deleted. The coordinates for the complex remain unchanged as originally submitted to the Brookhaven Protein Data Bank under accession number 1 pue.