Location of the triplex DNA-binding domain of Saccharomyces cerevisiae Stm1 protein.

Saccharomyces cerevisiae Stm1 protein (273 amino acids) is a purine motif triplex DNA-binding protein. Here, to examine the location of the triplex DNA-binding domain of Stm1 protein, we analyzed the interaction between the purine motif triplex and a series of truncated Stm1 proteins by electrophoretic mobility shift assay. Stm(1-113) (amino acids 1-113) was able to bind with the purine motif triplex. Smaller regions in Stm(1-113), Stm(1-54) (amino acids 1-54) and Stm(55-113) (amino acids 55-113), were unable to bind with the purine motif triplex. Although Stm(1-113) has the ability to bind with the purine motif triplex, it was unable to bind with the duplex. We conclude that Stm(1-113) is the minimal domain to specifically bind with the purine motif triplex.