domains might function in the innate immune system, possibly as lipopolysaccharide-binding domains [1,5]. The strongest argu- ment in favor of this assumption was that Limulus factor C has high affinity for lipopolysaccharides and serves in recognition of gram- negative bacteria. Another line of evidence for this assumption came from a survey of structural and functional information about Lgl1, a late gestation lung protein containing two LCCL-domains [1]. Our analyses suggested that Lgl1 protein might play an important role in host defense against microbial infection by recognizing polysaccharides of invading pathogens [1]. Recent studies have confirmed that the Lgl1 protein (renamed as Cysteine-Rich Secre- tory Protein LCCL Domain containing 2, CRISPLD2) has high affinity for lipopolysaccharide and plays a critical role in defense against endotoxin shock [6].
In the present work we tested the hypothesis that the LCCL- domains of CRISPLD2 may be involved in the binding of lipopoly- saccharide by this protein. Our results show that both LCCL- domains of human CRISPLD2 protein have high affinity for lipid A, the toxic moiety of lipopolysaccharides.