HCoV-HKU1 (isolate N5) Spike Trimer, His Tag (SPN-H52H5) is the ectodomain of HCoV-HKU1 (isolate N5) spike protein which contains AA Ala 13 - Asn 1276 (Accession # Q0ZME7-1). The recombinant protein is expressed from human 293 cells (HEK293) with T4 fibritin trimerization motif and a polyhistidine tag at the C-terminus. The S1/S2 furin-recognition site 752-RRKRR-756 is mutated to GGSGS to generate the uncleaved protein. Proline substitutions (N1067P, L1068P) are introduced to stabilize the trimeric prefusion state of the spike protein.