Lipoproteins

Conformational studies of an amphipathic peptide corresponding to human apolipoprotein A‐II residues 18‐30 with a C‐terminal lipid binding motif EWLNS

“…Enzyme activity of the exchangeable apolipoproteins have been correlated with lipid association and a concomitant increase in helical content (64). Because the exchangeable apolipoproteins (i) associate, (ii) become more helical and (iii) express biological activity in the presence of DMPC, this phospholipid has been extensively used to model the lipoprotein environment when studying apolipoproteins (65,66), apolipoprotein fragments (13, 14, 67) and de novo peptide mimics of apolipoproteins (2 1 ), However, lipoproteins are spherical particles composed of an outer phospholipid monolayer (66,68) while DMPC forms phospholipid bilayers as a vesicle or disc (69). ApoA-11( 18-30) + interacts more strongly with lipid micelles than with DMPC, adopting more than twice the helical structure in the former lipids.…”

ELECTRON PARAMAGNETIC RESONANCE STUDIES ON SPIN‐LABELLING OF PEPSIN: EFFECTS OF TEMPERATURE, pH AND UREA ON ITS CONFORMATION

“…The technique has proved useful in the study of active site geometry and the conformation of enzymes. For example, a-chymotrypsin was spin-labelled at the active site of serine, and denaturation with guanidine hydrochloride of different concentrations was studied by Morrisett et al (2). The geometry of the active site of lysozyme, namely the distance from the spin-labelled tryptophan-123 to an acetamide methyl group of a bound saccharide and to a C-2 proton of histidine-15, or the distance be-tween a spin-labelled inhibitor .and a C-2 proton of histidine-1 5 was estimated by studying changes in the relaxation rates of the protons in the presence of nitroxide radicals using n.m.r.…”