Recombinant Mouse CL-P1/COLEC12 Protein, CF

Collectins are a family of Ca⁺⁺-dependent, C-type lectins that contain a collagenous domain and function as recognition molecules for molecular patterns found on pathogens (1 - 4). Collectin placenta 1 (CL-P1), also known as collectin sub-family member 12 and scavenger receptor with C-type lectin type I (SRCL), is a 140 kDa member of the collectin family of glycoproteins. With two exceptions, all collectins are secreted. CL-P1 is the only collectin known to be membrane bound, while CL-L1 (collectin liver-1) is the only known cytoplasmic collectin (1). Mouse CL-P1 is synthesized as a 742 amino acid (aa) type II transmembrane glycoprotein that includes an N-terminal 39 aa cytoplasmic domain, an 18 aa transmembrane segment, and a 685 aa C-terminal extracellular domain. The short cytoplasmic domain contains an internalization motif (Y-K-R-F), while the ECD is complex, demonstrating a coiled-coil segment, a Ser-Thr rich region, a collagen-like structure, and a C-type lectin/carbohydrate recognition domain (CRD) (5, 6). Unlike human CL-P1, no splice variants of mouse CL-P1 have been described (5, 7). Trimerization of CL-P1 is mediated by its collagen-like and coiled-coil helical domains (1, 6). Within the ECD, mouse CL-P1 shares 88%, 89%, 92%, and 98% aa sequence identity with bovine, canine, human, and rat CL-P1, respectively. The CRD shares 23 - 27% aa sequence identity with the CRD of collectins CL-L1, collectin sub-family member 11, MBL, SP-A1, and SP-D. Notably, this CRD recognizes galactose and fucose within the context of asialo-orosomucoids associated with the Lewis^x epitope (8, 9). CL-P1 is expressed in vascular endothelial cells and may play a role in bacterial recognition or as a scavenger receptor for desialylated glycoproteins (6, 8).