The C terminus of apolipoprotein A-V modulates lipid-binding activity.
Human apolipoprotein A-V (apoA-V) is a potent modulator of plasma triacylglycerol (TG) levels. To probe different regions of this 343-amino-acid protein, four single Trp apoA-V variants were prepared. The variant with a Trp at position 325, distal to the tetraproline sequence at residues 293-296, displayed an 11-nm blue shift in wavelength of maximum fluorescence emission upon lipid association. To evaluate the structural and functional role of this C-terminal segment, a truncated apoA-V comprising amino acids 1-292 was generated. Far UV circular dichroism spectra of full-length apoA-V and apoA-V-(1-292) were similar, with approximately 50% alpha-helix content. In guanidine HCl denaturation experiments, both full-length and truncated apoA-V yielded biphasic profiles consistent with the presence of two structural domains. The denaturation profile of the lower stability component (but not the higher stability component) was affected by truncation. Truncated apoA-V displayed an attenuated ability to solubilize l-alpha-dimyristoylphosphatidylcholine phospholipid vesicles compared with full-length apoA-V, whereas a peptide corresponding to the deleted C-terminal segment displayed markedly enhanced kinetics. The data support the concept that the C-terminal region is not required for apoA-V to adopt a folded protein structure, yet functions to modulate apoA-V lipid-binding activity; therefore, this concept may be relevant to the mechanism whereby apoA-V influences plasma TG levels.
Beckstead
Jennifer A
JA
Center for Prevention of Obesity, Diabetes, and Cardiovascular Disease, Children's Hospital Oakland Research Institute, Oakland, California 94609, USA.
Wong
Kasuen
K
Gupta
Vinita
V
Wan
Chung-Ping L
CP
Cook
Victoria R
VR
Weinberg
Richard B
RB
Weers
Paul M M
PM
Ryan
Robert O
RO
D000072040:Apolipoprotein A-V; D001054:Apolipoproteins A / Q000097:blood / Q000737:chemistry* / Q000235:genetics; D002942:Circular Dichroism; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D008081:Liposomes / Q000737:chemistry*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary / Q000235:genetics; D011994:Recombinant Proteins; D014280:Triglycerides / Q000097:blood
C437704:APOA5 protein, human; D000072040:Apolipoprotein A-V; D001054:Apolipoproteins A; D008081:Liposomes; D011994:Recombinant Proteins; D014280:Triglycerides; D004134:Dimyristoylphosphatidylcholine