CRYSTAL-STRUCTURE OF HEMOLIN - A HORSESHOE SHAPE WITH IMPLICATIONS FOR HEMOPHILIC ADHESION

Hemolin, an insect immunoglobulin superfamily member, is a Lipopolysac charide-binding immune protein induced during bacterial infection. The 3.1 angstrom crystal structure reveals a bound phosphate and patches of positive charge, which may represent the Lipopolysaccharide binding site, and a new and unexpected arrangement of four immunoglobulin-lik e domains forming a horseshoe. Sequence analysis and analytical ultrac entrifugation suggest that the domain arrangement is a feature of the L1 family of neural cell adhesion molecules related to hemolin. These results are relevant to interpretation of human L1 mutations in neurol ogical diseases and suggest a domain swapping model for how L1 family proteins mediate hemophilic adhesion.