May I ask how to superimpose the overall structures of two analogues? e.g., the E. coli sliding clamp beta is a ring-shaped homodimer (two chains), while the yeast sliding clamp PCNA is a ring-shaped homotrimer (three chains), and their overall structures are quite similar, but when I use the matchmaker to superimpose them, it seems always only use the chain A, but not the all chains, pls see figures below~ Stay safe and warm, Many thanks!