TTC1, also known as tetratricopeptide repeat protein 1, is composed of 292 amino acids with three TPR motifs, as a Galpha16-binding protein. The interaction was confirmed both in vitro and in transfected mammalian cells, where TTC1 also binds to several other Galpha proteins. TTC1 was found to interact with Ha-Ras preferentially in its active form. Recombinant human TTC1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography.