Fig. 4. The role of K16 is the F-pocket nature dependent.
a The sequence of Tsn loop11–20 mutants. b, c upper panel: Relative activity of tapasin loop11–20 mutants to catalyze peptide exchange compared to ERp57-TsnWT towards A*03:01 and B*27:09. FTIC-KK9 was used for A*03:01, FTIC-IF9 (IRAAKFITCPPLF) was used for better resolution of B*27:09. Error bars (SD) were calculated from three independent experiments. For comparison of loop mutants to WT, the two-sample unequal variance Student’s t test was performed (*p < 0.05, **p < 0.01, ***p < 0.001). Lower panel: Representative peptide exchange profiles of 500 nM A*03:01/photoKK9, and B*27:09/photoRL9 in the absence (black) and presence of equimolar amounts of tapasin loop mutants. dFP means the baseline was subtracted. These curves were recorded on the PerkinElmer VICTOR3V machine.