Fig. 1. Sequence alignment of 20S proteasome α-subunit N-terminal residues. The seven (α1–α7) subunits of yeast (Sc) and human (Hs) proteasomes are shown with the single α-subunit of the T.acidophilum proteasome. The four conserved residues that stabilize the open gate conformation are shown on a yellow background. Other conserved residues generally perform obvious structural roles that do not change between open and closed proteasome conformations.