Fig. 8.

Models of the putative structures of the two tetrameric conformers of RNase A. In the subunits 1, 2, 3, 4 of both models the N- and C-terminal ends are shown as half circles and quarter circles. The N- and C-termini of each monomer involved in the domain-swapping mechanism are labeled and slightly removed from the labeled (1, 2, 3, 4) "core"-domain (full circles) of each subunit. A, model of RNase A; B, model of RNase A minor dimer (Liu et al. 1998); C, model of RNase A major dimer, and D, putative model of an RNase A trimer (Liu et al. 2001).