Sequence comparison and homology model of the SPT1 mutant protein of LY-B cells. (A) Protein sequences of SPT1 were compared from LY-B cells, CHO, human, mouse and S. cerviceae using T-coffee. The point mutation G246R in LY-B cells is indicated by an asterisk. (B) This homology model for mutant SPT1 from LY-B cells was prepared using Modeller v6.1. The illustrated figure shows the G246R mutation (indicated in a ball and stick representation) to be located in a pocket of hydrophobic residues (Phe279, Leu282, Val289, Leu247) was visualized by VMD.