Fig. 4.

Insertion loop in Sc_IGPD. (A) The 24-residue insertion loop in Sc_IGPD, situated between β2 and β4 colored in purple and the C-terminal inhibitor/substrate binding loop is shown in gray. The insertion (purple) within Sc_IGPD lies next to the C-terminal substrate/inhibitor binding loop (gray), possibly stabilizing the interaction. The 24-residue insert in Sc_IGPD compared with At_IGPD forms an additional β-strand (β3) between A44 and Q46, and therefore there is one extra strand within its external β-sheet. Residues between K38 and A44 are not well resolved within the EM map, and have not been modeled, and some residues in the loop region have been truncated because of poor side chain density. (B) The equivalent view in At_IGPD with a much smaller loop between β2 and β3, which is well defined in the EM map (shown in purple). The C-terminal loop (gray) is more poorly defined and makes no interactions with the loop region between β2 and β3.