Tandem affinity purification of protein complexes from mammalian cells by the Strep/FLAG (SF)-TAP tag

Isolation and dissection of native multiprotein complexes is a central theme in functional genomics. The development of the tandem affinity purification (TAP) tag has enabled efficient and large-scale purification of native protein complexes. The SF-TAP tag, a modified version of the TAP tag, allows a fast and straightforward purification of protein complexes from mammalian cells. It consists of a tandem Strep-tag II and a FLAG epitope (SF-TAP). The SF-TAP tag allows a native elution of protein complexes without proteolytic cleavage needed in the original TAP procedure. Besides the SF-TAP protocol, the principal idea of a pathway mapping by subsequent tagging of copurified proteins is demonstrated for the interactome of the MAPKKK Raf.