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Updated: Aug 1, 2026

Mapping the Binding Site of an Aptamer on ATP Using MicroScale Thermophoresis
Published on: January 7, 2017
Substrate specificity of allelic variants of the TAP peptide transporter
1Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139.
Abstract:
The transporter associated with antigen processing (TAP) translocates peptides from the cytosol into the lumen of the endoplasmic reticulum (ER). An important determinant for the specificity of translocation is the identity of the C-terminal residue of the peptide substrate. In the rat, a suitable C terminus is necessary but not always sufficient for a peptide to be selected for translocation. Here we show that sequence constraints within a peptide of optimal length (9 residues) may interfere with transport; that the transporter selectively translocates shorter derivatives of a 16-mer peptide rather than the 16-mer itself; and that the transporter cimb allele, which is most selective in the C termini it will tolerate, is more relaxed in peptide length preference than is the clma variant.
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