Figure S1. Sequence alignment of N-terminal regulatory domains of selected SUS enzymes. The numbering scheme and secondary structure profile at the top of the alignment refers to the AtSus1 structure. Shown in the alignment are sp|P49040|SUS1_ARATH (AtSus1), emb|CAB89040.1|SUS4_ARATH (Arabidopsis thaliana SUS4), emb|CAB40794.1|SUS_MEDTR (Barrel Clover), gb|AAC28107.1|SUS_PISSA (garden pea), sp|P13708.2|SUSY_SOYBN (soy bean), tr|E9KNH1|SUS1_POPTO (poplar), gb|ACV72640.1|SUS1_GOSHI (cotton), sp|P10691.1|SUS1_SOLTU (potato), sp|P31922|SUS1_HORVU (barley), sp|P30298.2|SUS1_ORYSJ (rice), sp|P04712.1|SUS1_MAIZE (maize), emb|CAA04543.1|SUS_TRIAE (common wheat). Conserved amino acids are shown in four levels of green, the two conserved phosphorylation sites, Ser13 and Ser167, are denoted by red triangles, and the site of thiolation, Cys266, is marked by a black triangle. The residues involved in the A:D interface are highlighted in blue boxes, while the residues at the A:B interface are in black boxes. Figure S2. Topology diagram of the GT-B glycosyltransferase domain in AtSus1. The secondary structural elements for the GT-BN domain are shown in purple and for the GT-BC domain are in blue. The nomenclature for denoting the secondary structural elements is derived from Ha et al. (44) for MurG; the helical extension (helix Nα7) is unique to sucrose synthases. Figure S3. A stereo view of the CTD in subunit H in AtSus1 complexed with UDP and fructose. The polypeptide is represented as sticks: the carbon atoms from residue 11-28 in the CTD are colored in magenta, the rest of the CTD is in cyan, and the polypeptide chain outside of the CTD is in grey. The region of the 2Fo-Fc electron density map surrounding the CTD is contoured at 0.95 σ; α1 helix is labeled.

Figure S1

Figure S2

Figure S3