Sequence-specific H-1 NMR resonance assignments and secondary structure ofhuman apolipoprotein C-I in the presence of sodium dodecyl sulfate

Apolipoprotein (apo) C-I is a 57-residue exchangeable plasma protein distri buted mainly in high and very low density lipoprotein. In this report we pr esent the nuclear magnetic resonance spectra of native apoC-I and synthetic apoC-I, containing selected N-15-labelled amino acids, in the presence of sodium dodecyl sulfate. The proton resonances of apoC-I are assigned and th e secondary structure is estimated from the difference of measured cc-proto n chemical shifts to random coil values and the observed NOE interactions. According to these data apoC-I forms two helices, Val-4-Lys-30 and Leu-34-L ys-52, linked by an unstructured region Gln-31-Glu-33. The N-terminal segme nts of each helix, Val-4-Gly-15 and Leu-34-Met-38, appear to be more flexib le than the helical core regions Asn-16-Lys-30 and Arg-39-Lys-52.