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Published online before print August 31, 2007
Protein Science, DOI: 10.1110/ps.073041107
 Copyright © 2007 The Protein Society
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Conformational changes induced by a single amino acid substitution in the trans-membrane domain of Vpu: Implications for HIV-1 susceptibility to channel blocking drugs

Sang Ho Park and Stanley J. Opella

Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0307, USA

(RECEIVED May 29, 2007; FINAL REVISION June 27, 2007; ACCEPTED June 28, 2007)

The channel-forming trans-membrane domain of Vpu (Vpu TM) from HIV-1 is known to enhance virion release from the infected cells and is a potential target for ion-channel blockers. The substitution of alanine at position 18 by a histidine (A18H) has been shown to render HIV-1 infections susceptible to rimantadine, a channel blocker of M2 protein from the influenza virus. In order to describe the influence of the mutation on the structure and rimantadine susceptibility of Vpu, we determined the structure of A18H Vpu TM, and compared it to those of wild-type Vpu TM and M2 TM. Both isotropic and orientationally dependent NMR frequencies of the backbone amide resonance of His18 were perturbed by rimantadine, and those of Ile15 and Trp22 were also affected, suggesting that His18 is the key residue for rimantadine binding and that residues located on the same face of the TM helix are also involved. A18H Vpu TM has an ideal, straight {alpha}-helix spanning residues 6–27 with an average tilt angle of 41° in C14 phospholipid bicelles, indicating that the tilt angle is increased by 11° compared to that of wild-type Vpu TM. The longer helix formed by the A18H mutation has a larger tilt angle to compensate for the hydrophobic mismatch with the length of the phospholipids in the bilayer. These results demonstrate that the local change of the primary structure plays an important role in secondary and tertiary structures of Vpu TM in lipid bilayers and affects its ability to interact with channel blockers.

Keywords: ion channel; viroporin; HIV; channel blocker; micelles; bicelles; solid-state NMR

Reprint requests to: Stanley J. Opella, Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307, USA; e-mail: sopella{at}ucsd.edu; fax: (858) 822-4821.

Article published online ahead of print. Article and publication date are at http://www.proteinscience.org/cgi/doi/10.1110/ps.073041107.


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