SP-D (Surfactant Protein-D, PSP-D)

Size

£832.00

SKU:: 059467
Purity:: Purified by Protein A affinity chromatography from hybridoma culture supernatant.
Storage Conditions:: -20°C
Supplier:: United States Biological
Host:: Mouse
Immunogen:: Recombinant protein corresponding to Ala21-Phe375 of human SP-D, expressed in NS0 cells.
Clone:: 26G3
Format:: Supplied as a lyophilized powder from PBS, 5% trehalose. Reconstitute with 500ul sterile PBS.
Extra Details:: SP-D (surfactant protein-D; also PSP-D) is a 43kD member of the collectin family of innate immune modulators. It is constitutively secreted by alveolar lining cells and epithelium associated with tubular structures. Its principal components consist of a collagen-like region and a C-terminal carbohydrate recognition domain (CRD), a structure that further places it in a subset of an expanded group of proteins termed defense collagens (1‑4). Human SP-D is synthesized as a 375aa precursor. It contains a 20 aa signal sequence and a 355aa mature region. The mature molecule is characterized by the presence of a 25aa N-terminal linking-region, a 177aa hydroxyproline and hydroxylysine collagen-like domain, a 46aa coiled-coil segment, and a 106 aa, C-terminal collectin-like C-type lectin domain (CRD) (5, 6). Two additional, potential isoforms exist. One shows a 13aa N-terminal extension, while the other combines the N-terminal extension with a deletion of aa’s 206‑375. Mature human SP-D shares 75% and 78%aa identity with mouse and pig SP-D, respectively. Monomeric SP-D is unusual (3). The basic form of SP-D is that of a glycosylated, disulfide-linked 150kD trimer that generates an alpha-helical coiled-coil structure linked to a “head” of three symmetrical CRDs (4, 7). Each CRD recognizes the hydroxides of one monosaccharide (4). Trimerization allows for the discrimination of monosaccharide patterns specific to microbial pathogens (7). Typically, SP-D forms a higher-order 620kD, X-shaped dodecamer through disulfide bonds associated with the N-terminus (8). This allows for even finer discrimination of self vs. nonself carbohydrate patterns, and facilitates binding to complex antigens (8, 9). One polymorphism, a Met11‑Thr11 transition in human, apparently precludes the formation of oligomers, potentially affecting the ability of affected individuals to interact with microorganisms (9, 10). Finally, SP-D is known to bind both SIRP alpha and the calreticulin/CD91 complex on macrophages. When the ratio of antigen/pathogen to available CRDs is low, antigen can be bound without occupying all available CRDs. The free CRDs will bind to SIRP alpha, generating a signal that downmodulates the inflammatory response. When virtually all CRDs are occupied by ligand, however, free CRDs are not available for SIRP alpha binding. Instead, the dodecamer is depicted to undergo a structural rearrangement, exposing the N-termini of all four linked trimers. This exposed terminus is known to bind to the calreticulin/CD91 complex, an event that initiates inflammation. Thus, it would appear that SP-D allows for a graded response to environmental challenge. SP-D provides a mechanism for the clearance of small antigenic insults without the need for a damaging inflammatory response (3). Applications: Suitable for use in ELISA. Other applications not tested. Recommended Dilutions: ELISA (capture): using 059466 as detection antibody. Optimal dilutions to be determined by the researcher. Storage and Stability: Lyophilized and reconstituted products are stable for 12 months after receipt at -20°C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.

Shipping Conditions:: Blue Ice