Characterisation of CL-K1 fragments containing disease-associated mutations. A) Gel filtration on a Superdex 200 (10/30 column) in 50 mM Tris–HCl at pH 7.4, containing 150 mM NaCl. The elution positions of conalbumin (75 kDa), ovalbumin (44 kDa) and ribonuclease A (13.7 kDa) are indicated. Top, The wild-type CL-K1 fragment interacts with the column matrix in buffer containing Ca2+ (2 mM) but not in the absence of Ca2+ (2 mM EDTA) or in the presence of inhibitory concentrations of mannose (200 mM). Bottom, None of the three CL-K1 variants interacts with the column, even in the presence of Ca2+. B) CD spectra of the wild-type CL-K1 fragment and the disease-associated CL-K1 variants. C) Binding of biotinylated invertase to full length CL-K1 and trimeric fragments. Values are the mean ± error from duplicate measurements. Tighter binding of the full-length protein is due to its increased avidity. CL-K1, collectin-K1; EDTA, ethylenediaminetetraacetic acid.