Conformational studies of the N‐terminal lipid‐associating domain of human apolipoprotein C‐I by CD and 1H NMR spectroscopy

A peptide comprising the N‐terminal 38 residues of human apolipoprotein C‐I (apoC‐I(1‐38)) was synthesized using solid‐phase methods and its solution conformation studied by CD and 1H NMR spectroscopy. The CD data indicate that apoC‐I(1‐38) has a similar helical content (55%) in the presence of saturating amounts of SDS or egg yolk lysophosphatidylcholine. A structural ensemble of SDS‐bound apoC‐I(1‐38) was calculated from 464 NOE‐based distance restraints using distance geometry methods. ApoC‐I(1‐38) adopts a helical structure between residues V4 and K30 and an extended C‐terminus from Q31 when associated with SDS. The region K12‐G15 undergoes slow conformational exchange as indicated by above‐average amide resonance linewidths, large temperature coefficients, and fast exchange (