Studies of the aggregation behavior of HIV-1 Vif Protein
Hakansson, Susanna L.
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Lentivirus Vif proteins are potent regulators of virus infectivity; however, little is known about their functional domains. Vif (viral infectivity factor), a 23-kDa protein encoded by the human immunodeficiency virus type 1 (HIV-1), has been shown to be important for virion infectivity. Structural information would be of great importance to fully understand this protein. Wild type Vif exists in solution as aggregates, unsuitable for structural studies by x-ray crystallography or NMR. The tendency of a protein to aggregate has previously been changed by a single point mutation to allow structural determination. In an attempt to improve the solubility of the Vif protein, this strategy was applied. Point mutations, replacing hydrophobic residues with either alanine or lysine, and deletion mutants of the N-terminal region were made. None of the mutations had a profound effect on V if s solubility. In the second part of this project, the problematic aggregation behavior of Vif was studied using NMR. The refolding of Vif in different concentrations of Guanidine-hydrochloride (Gu-HCl) and the initial steps in the refolding path were looked at. Two-dimensional (2D) proton nitrogen-15 heteronuclear single quantum coherence (HSQC) spectra of Vif in different concentrations of Gu-HCl were collected. The disappearance and decrease of peak intensity was observed before any peak movement was detected. This strongly suggests that Vif is aggregating as it is refolding, precluding any structural studies.