Structural features of apolipoprotein A1 in HDLs and in complexes with DMPC. Low temperature ESR study
N. V. Medvedeva, A. Yu. Misharin
Cardiology Research Centre, Academy of Medical Sciences of the USSR, Moscow
Apolipoprotoin A1 (apoA1) was labelled with the excess of 2,2,6,6-tetramethylpi-peridinyl-N-oxyl-4-(2,4-dichloro-l,3,5-triazinyl-6)-aminc at pH 9.8. The products, containing 7.2 (±1) paramagnetic labels per 1 molecule of apoA1, showed spin-spin and dipole-dipole exchange interactions. The ESR spectra of the spin labelled A1 (at 77K) had d1/d values 0.76 (at pH 7.4), 0.59 (in 3 M NaCl), 0.55 (in 3 M guanidinium hydrochloride), 0.44 (in 40% 2-chloroethanol).
Micellar complexes of spin labelled apoA1/DMPC (1:20 mol/mol and 1:190 mol/mol) and HDL containing spin labelled apoA1 were prepared. Comparison of ESR spectra at 77 K showed that apoAl structure varies in the complexes with different stoichionietry and in spin labelled HDL. These data show the importance of hydrophobia protein-protein interactions for the structure of HDL and synthetic complexes of apoA1 with phosphatidyl choline.
Russian Journal of Bioorganic Chemistry 1991, 17 (1):60-65