THE SOLUTION STRUCTURE OF THE ACTIVE DOMAIN OF CAP18 - A LIPOPOLYSACCHARIDE-BINDING PROTEIN FROM RABBIT LEUKOCYTES

We have employed the circular dichroism (CD) technique to characterize the solution structure of CAP18(106-137), a Lipopolysaccharide (LPS) binding, antimicrobial protein, and its interaction,vith lipid A, Our results revealed that CAP18(106-137) may exist in at least three lipid A concentration-dependent, primarily helix conformations. The 'model' structure of CAP18(106-137) in 30% (v/v) TFE, determined by nuclear m agnetic resonance (NMR) technique, was found to be a complete and very rigid helix, In this conformation, the cationic and hydrophobic group s of CAP18(106-137) are separated into patches and stripes in such a w ay that it can favorably interact with Lipid A through either coulombi c interaction with the diphosphoryl groups or hydrophobic interaction with the fatty acyl chains.