A chirality change in XPC- and Sfi1-derived peptides affects their affinity for centrin

Abstract

The Ca2+-binding protein centrin binds to a hydrophobic motif (W1xxL4xxxL8) included in the sequence of several cellular targets: XPC (xeroderma pigmentosum group C protein), Sfi1 (suppressor of fermentation-induced loss of stress resistance protein1), and Sac3 [the central component of the transcription and mRNA export (TREX-2) complex]. However, centrin binding occurs in a reversed orientation (L8xxxL4xxW1) for Sfi1 and Sac3 compared with XPC. Because d-peptides have been investigated for future therapeutic use, we analyzed their centrin-binding properties. Their affinity for centrin was measured using isothermal titration calorimetry. The chirality change in the target-derived peptides affected their ability to bind centrin in a specific manner depending on the sequence orientation of the centrin-binding motif. In contrast to l-XPC-P10, d-XPC-P10 bound C-HsCen1 in a Ca2+-dependent manner and to a lesser extent. d-XPC-P10 exhibited a reduced affinity for C-HsCen1 (Ka=0.064×106M−1) by a factor of 2000 compared with l-XPC-P10 (Ka=132×106M−1). d-peptides have a lower affinity than l-peptides for centrin, and the strength of this affinity depends on the sequence orientation of the target-derived peptides. The residual affinity observed for d-XPC suggests that the use of d-peptides represents a promising strategy for inhibiting centrin binding to its targets.