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The N-Terminus of Apolipoprotein A-V Adopts a Helix-Bundle Molecular Architecture
Biochemistry (2008)
  • Kasuen Wong, University of California - Berkeley
  • J. A. Beckstead
  • D. Lee
  • P. M.M. Weers
  • E. Guigard, University of Alberta
  • C. M. Kay, University of Alberta
  • R. O. Ryan, University of California - Berkeley

Previous studies of recombinant full-length human apolipoprotein A-V (apoA-V) provided evidence of the presence of two independently folded structural domains. Computer-assisted sequence analysis and limited proteolysis studies identified an N-terminal fragment as a candidate for one of the domains. C-Terminal truncation variants in this size range, apoA-V(1-146) and apoA-V(1-169), were expressed in Escherichia coli and isolated. Unlike full-length apoA-V or apoA-V(1-169), apoA-V(1-146) was soluble in neutral-pH buffer in the absence of lipid. Sedimentation equilibrium analysis yielded a weight-average molecular weight of 18811, indicating apoA-V(1-146) exists as a monomer in solution. Guanidine HCl denaturation experiments at pH 3.0 yielded a one-step native to unfolded transition that corresponds directly with the more stable component of the two-stage denaturation profile exhibited by full-length apoA-V. On the other hand, denaturation experiments conducted at pH 7.0 revealed a less stable structure. In a manner similar to that of known helix bundle apolipoproteins, apoA-V(1-146) induced a relatively small enhancement in 8-anilino-1-naphthalenesulfonic acid fluorescence intensity. Quenching studies with single-Trp apoA-V(1-146) variants revealed that a unique site predicted to reside on the nonpolar face of an amphipathic R-helix was protected from quenching by KI. Taken together, the data suggest the 146 N-terminal residues of human apoA-V adopt a helix bundle molecular architecture in the absence of lipid and, thus, likely exist as an independently folded structural domain within the context of the intact protein.

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Copyright © 2008 American Chemical Society. The definitive version is available at
Citation Information
Kasuen Wong, J. A. Beckstead, D. Lee, P. M.M. Weers, et al.. "The N-Terminus of Apolipoprotein A-V Adopts a Helix-Bundle Molecular Architecture" Biochemistry Vol. 47 Iss. 33 (2008)
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