Figure 1.

SF3b1 and Tat-SF1 splicing factors contain ULM and UHM motifs. Human Tat-SF1 (A, blue) and SF3b1 (B, green) domain organization are shown. Residue ranges of constructs used for crystallization (structure) or isothermal titration calorimetry (ITC) are given in parentheses. p14, p14a binding site. C, the aligned sequences of five ULM repeats from human SF3b1 are shown in the inset below. The boundaries of synthetic peptides (in parentheses and underlined) terminate at the second TP motif, which for ULM1/ULM2 and ULM2/ULM3 also corresponds to the start of the next ULM. The central tryptophan (yellow) is preceded by characteristic basic (R/K) amino acids (green).