Conformation and Interactions of Uteroglobin Fragments 4-14 and 49-65 In Aqueous-solution Containing Surfactant Micelles

The conformation of two fragments of rabbit uteroglobin is described. The peptides are PRFAHVIENLL and PQTTRENIMKLTEKIVK, corresponding to helices I and IV in the crystal structure. CD shows that both peptides interact with sodium dodecyl sulfate (SDS) micelles and change their conformation to an alpha-helix. The helical content estimated from the CD band at 222 nm is about 40% in each peptide. Surface tension measurements show that both peptides lower the critical micellar concentration (cmc) of SDS, with a more dramatic effect in the case of helix I. This peptide by itself acts as a surfactant, and is able to interact with SDS even below the observed cmc, forming beta aggregates. Proton magnetic resonance (H-1-nmr) suggests that flexible helices are present. The longest helical stretches compatible with H-1-nmr data extend from 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.