Affinity and kinetic analysis of the bovine plasma C‐type lectin collectin‐43 (CL‐43) interacting with mannan

TLDR

Collectins are C‑type lectins that contribute to innate immunity by binding microbial carbohydrates through their lectin domains. Using surface plasmon resonance, the authors measured real‑time binding of purified bovine CL‑43, a trimeric collectin of 99.8 kDa, to immobilized yeast mannan. CL‑43 exhibited rapid dissociation (1.19–1.36 × 10⁻² s⁻¹), high association (4.37–5.07 × 10⁵ M⁻¹ s⁻¹), and a strong affinity with K_D of 2.68–2.72 × 10⁻⁸ M.

Abstract

Collectins are C‐type lectins which have been implied to play an important role in the innate immune defence against microorganisms. The critical discriminatory event in the opsonization of microorganisms by collectins is the interaction of the C‐type lectin domain with microbial carbohydrates. Surface plasmon resonance measurements allow for quantitative real‐time measurements of binding interaction between immobilized carbohydrate and unlabelled lectin in solution. Binding analysis were carried out with purified collectin‐43 (CL‐43) which structurally is the simplest collectin consisting of only three polypeptides each terminating in a C‐type lectin domain. The target was immobilized yeast mannan. The molecular mass of native CL‐43 was determinated by mass spectroscopy to 99.8 kDa. The dissociation rate ( k diss ) of the C‐type lectin‐carbohydrate binding was fast (1.19–1.36 × 10 −2 second −1 ), and the association rate ( k ass ) was 4.37–5.07 × 10 5 M −1] second−1 . The equilibrium constant for dissociation ( K d ) was 2.68–2.72 × 10 −8 M.