No secretion of variant CL-K1s containing mutations associated with 3MC syndrome. A) Structure of the CRD of CL-K1 showing the position of mutations associated with 3MC syndrome. Secondary structure features are labelled based on the structure of MBL . Polar interactions are indicated by dotted lines. B) Secretion of wild type and variant CL-K1s from mammalian cells. Serum-free medium from Chinese hamster ovary cells (20 μL) transfected with wild-type (WT) or variant cDNAs was separated on a 15% SDS-PAGE gel under non-reducing conditions and blotted onto a nitrocellulose membrane. Secreted CL-K1 was detected using rabbit polyclonal anti-CL-K1 antibodies. Purified wild-type CL-K1 (approximately 20 ng) was used as a positive control. CL-K1, collectin-K1; CRD, carbohydrate-recognition domain; MBL, mannan-bindng lectin; 3MC, Carnevale, Mingarelli, Malpuech and Michels.