CONFORMATION AND INTERACTIONS OF UTEROGLOBIN FRAGMENTS 4-14 AND 49-65IN AQUEOUS-SOLUTION CONTAINING SURFACTANT MICELLES

The conformation of two fragments of rabbit uteroglobin is described. The peptides are PRFAHVIENLL and PQTTRENIMKLTEKIVK, corresponding to h elices I and IV in the crystal structure. CD shows that both peptides interact with sodium dodecyl sulfate (SDS) micelles and change their c onformation to an alpha-helix. The helical content estimated from the CD band at 222 nm is about 40% in each peptide. Surface tension measur ements show that both peptides lower the critical micellar concentrati on (cmc) of SDS, with a more dramatic effect in the case of helix I. T his peptide by itself acts as a surfactant, and is able to interact wi th SDS even below the observed cmc, forming beta aggregates. Proton ma gnetic resonance (H-1-nmr) suggests that flexible helices are present. The longest helical stretches compatible with H-1-nmr data extend fro m Phe(6) to Leu(14) for helix I and from Arg(53) to Ile(63) for helix IV. (C) 1993 John Wiley and Sons, Inc.