TWO HOMOLOGOUS REPEATS OF 88 AMINO ACIDS AT BOTH ENDS OF TBP FORM TWO DNA BINDING MOTIFS. THESE MOTIFS ARE MADE UP OF ANTIPARALLEL BETA SHEETS (5 STRANDS EACH) AND TWO HELICES. LOOPS THAT CONNECT BETA SHEETS 2 AND 3 FORM "STIRRUPS." THE OTHER 4 BETA SHEETS FROM EACH MOTIF INTERACT WITH THE DNA BY FORMING THE CONCAVE UNDERSIDE OF THE SADDLE SHAPED PROTEIN. RESIDUES FROM THE HELICES FORM THE LOOP THAT JOINS THE MOTIFS, BUT DO NOT INTERACT WITH THE DNA