Fig. 5.

Immunoprecipitation of SQM presenting the Myc epitope tag. The empty SQM scaffold protein (SQM) or SQM carrying a Myc peptide insert in each of the three available sites (N, loop 1 or loop 2) were expressed in E.coli. SQM with Myc inserted at the N-terminus also carried an AU1 tag in loop 1 and is designated SQM-Myc(N)AU1(1). SQM carrying Myc in loop 2 also carries the AU1 epitope insert in loop 1 [SQM-AU1(1)Myc(2)]. The variant carrying the Myc peptide in loop 1 did not have any other peptide inserts and is designated SQM-Myc(1). Each protein sample was incubated with immobilized anti-Myc antibody and proteins eluted from these columns were analysed with an antibody recognizing the S-tag present in the amino terminus of all our model peptide aptamers. Whereas SQM alone was not recruited to the anti-Myc antibody column, all of the other model peptide aptamers were, demonstrating that the Myc tag is available for interaction regardless of which insertion site is used.