Figure 5.

Features of the PSA3 protein. A, Multiple sequence alignment of PSA3 orthologs. The predicted transit peptide cleavage site in At-PSA3 is marked with an arrow. The region used as an antigen for the Zm-PSA3 antibody is marked above with a line. Cysteines that flank a predicted peptide-binding groove are marked with asterisks. The box marks the region of At-PSA3 that was deleted in the yeast two-hybrid assay shown in Figure 9A. Protein identifiers: ZmPSA3, GRMZM2G051403 (Zea mays, a monocot); AtPSA3, AT3G55250 (Arabidopsis thaliana, a dicot); PpPSA3, XP_001775451.1 (Physcomitrella patens, moss); CrPSA3, XP_001702929.1 (Chlamydomonas reinhardtii, green alga); AmPSA3, XP_006844955.2 (Amborella trichopoda, basal angiosperm). B, Predicted structure of PSA3. The structure of Zm-PSA3 was predicted by I-TASSER (Yang et al., 2015b) at http://zhanglab.ccmb.med.umich.edu/I-TASSER/). The ribbon diagrams to the left show the predicted structure from two angles, each with the bound peptide predicted by I-TASSER (purple, stick diagram). The Cys pairs that flank the predicted acidic groove are shown as yellow spheres. The transit peptide (TP) is marked. The three images to the right show electrostatic surface representations calculated with PyMol. The first two views highlight the acidic cleft shown from the same angles as the ribbon diagrams, and the third shows the “back” side of the protein where the acidic stripe continues and can be seen to be surrounded by a basic surface.