Pulmonary surfactant-associated polypeptide SP-C in lipid micelles: CD studies of intact SP-C and NMR secondary structure determination of depalmitoyl-SP-C(1-17).

The surfactant-associated polypeptide C (SP-C) is a 35-residue lipopolypeptide which is essential for the function of surfactants used for therapy of infant respiratory distress. Modeling based on the recently determined nuclear magnetic resonance (NMR) structure of native SP-C in an organic solvent showed that SP-C could readily insert into fluid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine bilayers. The present paper describes further physical-chemical studies of intact SP-C and its N-terminal 17-residue polypeptide fragment, depalmitoyl-SP-C(1-17), in the presence of dodecylphosphocholine micelles. The results obtained provide a link between the NMR solution structure and the behaviour of SP-C in an ordered lipid environment, and thus present new insights for rational design of SP-C analogs for therapeutic purposes.