Natural killer cells are white blood cells able to kill tumor, virus-infected or stressed cells. NKR-P1 is a C-type lectin like-receptor on surface of human natural killer cells and LLT1 is its binding partner belonging to the same structural family.
Recently, we have expressed, purified and solved four crystal structures of the extracellular part of LLT1 in monomeric, dimeric and hexameric form [1, 2]. In this contribution, we present three more structures characterizing this receptor-ligand binding pair: structures of the extracellular part of NKR-P1 in the fully glycosylated and deglycosylated form and a structure of the NKR-P1:LLT1 complex. Expression and purification of NKR-P1 was described by us recently as well .
All three crystal structures show NKR-P1 in a dimeric form with an unexpected dimerization mode. Unlike LLT1, which has the α2 helix in the dimerization interface, NKR-P1 dimer has the α1 helix in its dimerization interface. This different dimeric arrangement of both proteins enables spatial connection of NKR-P1 with LLT1 not only in a single molecular complex, but in a periodical chain of alternating receptor/ligand molecules. Such chain we really observe in the presented crystal structure.
Acknowledgement: This study was supported by BIOCEV (ERDF CZ.1.05/1.1.00/02.0109), Czech Science Foundation (15-15181S and 18-10687S), MEYS of the Czech Republic (LTC17065 within the COST Action CA15126), Charles University (UNCE 204025/2012, GAUK 161216), and Instruct (R&D pilot scheme APPID 56 and 286).