Changes in the secondary structure of apolipoprotein B-100 after Cu2+-catalysed oxidation of human low-density lipoproteins monitored by Fourier transform infrared spectroscopy.
Fourier transform infrared (FTIR) spectra have been obtained of human low-density lipoproteins (LDL) in H2O and 2H2O buffers. The absorption bands are assigned to vibrations of the lipid and apolipoprotein B-100 components. The analysis of second-derivative spectra allowed an assignment of individual protein bands to alpha-helical, random, coil or beta-structure and beta-turn conformations. Changes in the FTIR spectra after Cu2+-catalysed oxidation of the LDL particles indicate that the structure of apolipoprotein B-100 becomes less ordered, with some alterations of alpha-helical and beta-turn conformation. The main beta-structure absorption at 1620 cm-1 is unaffected by oxidation. Taking into account the resistance to oxidation and the slow H-2H exchange it is suggested that the beta-structure is hidden from external factors whereas other structures are mostly present on the surface of the LDL particle. Oxidation affects mainly the surface region of apolipoprotein B-100 and leads to a structural rearrangement which consequently changes the receptor specificity of the LDL.
Herzyk
E
E
Department of Biochemistry and Chemistry, Royal Free Hospital School of Medicine, London, U.K.
Lee
D C
DC
Dunn
R C
RC
Bruckdorfer
K R
KR
Chapman
D
D
D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000097:blood*; D003300:Copper / Q000494:pharmacology*; D005583:Fourier Analysis; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood*; D010084:Oxidation-Reduction; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared
D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D008077:Lipoproteins, LDL; D003300:Copper