Fig. 1

The pAC65 peptide binds to PD-L1 and disrupts the PD-L1/PD-1 and PD-L1/CD80 complexes. A-F 2D (¹H-¹⁵N SOFAST-HMQC) AIDA experiments. The spectra of apo-PD-1, characteristic signals boxed in green (A), a complex of PD-1 and PD-L1, characteristic signals disappeared – boxed in red (B), the sample after the addition of peptide pAC65 to the PD-1/PD-L1 complex in the molar ratio 1:1 (C), apo-PD-L1 (D), a complex of PD-L1 and CD80 (E), the sample after the addition of peptide pAC65 to the complex PD-L1/CD80 in the molar ratio 1:1 (F). The characteristic signals in the spectra of apo proteins are boxed in green ((A) and (D)); signals disappeared upon complexes formation, boxed in red ((B) and (E)); restored peaks after the addition of pAC65 to the protein complexes are boxed in green ((C) and (F)) G-I Crystal X-ray structure of the PD-L1/pAC65 complex (PDB: 8ALX). G Overall view of the PD-L1/pAC65 binding interface, hydrophobic interactions are shown in red, hydrophilic in blue, and residues that provide both types of interactions are colored in violet. H Detailed hydrophobic interactions of pAC65 at the binding interface. Color-coded as in panel G. I Detailed polar interactions of pAC65 at the binding interface. Color-coded as in panel G