Isolation of a novel variant of secretory component with low affinity to dimeric immunoglobulin a by immobilised metal ion affinity chromatography. (November 2021)

• Record Type: Journal Article
• Authors: Yamada, Kiyoshi; Mizukoshi, Nobutaka; Kawata, Aya; Ono, Megumi; Hizono, Terumasa; Hashimoto, Kei; Azuma, Norihiro
• Is Part Of: International dairy journal. Volume 122(2021)
• Publication Date: 2021-11
• Subjects: Dairying -- Periodicals; Industrie laitière -- Périodiques; Electronic journals; 338.1762142
• DOI: 10.1016/j.idairyj.2021.105103
• Languages: English
• ISSNs: 0958-6946

Abstract

Abstract: By applying immobilised metal affinity chromatography to a free secretory component (FSC) preparation from bovine milk, we identified a novel FSC variant with lower affinity to dimeric immunoglobulin A. Using cDNA analysis, we found a novel His to Arg mutation at the 81st residue where the amino acid is well conserved among species. The IgA-binding portion of polymeric immunoglobulin receptor (pIgR) consists of five Ig-like domains (D1–D5); the first complementarity-determining region (CDR1) of D1 is especially critical to the noncovalent binding of pIgR to IgA. The mutation at position 81 occurred within D1, but at the beginning of the E/F loop on the opposite side of CDRl; this region is located at the interface with D2. Given that residues in D2 may form hydrogen bonds with D1, the mutation to Arg may have caused a positive charge that disturbed hydrogen bonding, altered domain relative orientation, and thereby lowered affinity.