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Solution structure of the equine infectious anemia virus p9 protein: a rationalization of its different ALIX binding requirements compared to the analogous HIV-p6 protein.

Sharma A, Bruns K, Röder R, Henklein P, Votteler J, Wray V, Schubert U - BMC Struct. Biol. (2009)

Bottom Line: The structural elements identified for p9 differ substantially from that of the functional homologous HIV-1 p6 protein.However, p6 contains an additional PTAP L-domain that promotes HIV-1 release by binding to the tumor susceptibility gene 101 (Tsg101).The notion that structures found in p9 differ form that of p6 further support the idea that different mechanisms regulate binding of ALIX to primary versus secondary L-domains types.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Structural Biology, Helmholtz Centre for Infection Research, D-38124 Braunschweig, Germany. alok.sharma@gmail.com

ABSTRACT

Background: The equine infection anemia virus (EIAV) p9 Gag protein contains the late (L-) domain required for efficient virus release of nascent virions from the cell membrane of infected cell.

Results: In the present study the p9 protein and N- and C-terminal fragments (residues 1-21 and 22-51, respectively) were chemically synthesized and used for structural analyses. Circular dichroism and 1H-NMR spectroscopy provide the first molecular insight into the secondary structure and folding of this 51-amino acid protein under different solution conditions. Qualitative 1H-chemical shift and NOE data indicate that in a pure aqueous environment p9 favors an unstructured state. In its most structured state under hydrophobic conditions, p9 adopts a stable helical structure within the C-terminus. Quantitative NOE data further revealed that this alpha-helix extends from Ser-27 to Ser-48, while the N-terminal residues remain unstructured. The structural elements identified for p9 differ substantially from that of the functional homologous HIV-1 p6 protein.

Conclusions: These structural differences are discussed in the context of the different types of L-domains regulating distinct cellular pathways in virus budding. EIAV p9 mediates virus release by recruiting the ALG2-interacting protein X (ALIX) via the YPDL-motif to the site of virus budding, the counterpart of the YPXnL-motif found in p6. However, p6 contains an additional PTAP L-domain that promotes HIV-1 release by binding to the tumor susceptibility gene 101 (Tsg101). The notion that structures found in p9 differ form that of p6 further support the idea that different mechanisms regulate binding of ALIX to primary versus secondary L-domains types.

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Schematic comparison of the Tsg101- and ALIX-binding domains of p6 and p9 in relation to the experimentally determined secondary structures in 50% TFE.
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Figure 8: Schematic comparison of the Tsg101- and ALIX-binding domains of p6 and p9 in relation to the experimentally determined secondary structures in 50% TFE.

Mentions: In their most structured states both molecules possess stable secondary structure although neither molecule possesses a stable tertiary structure. In a hydrophobic environment at low pH, both adopt helical secondary structure in their C-termini, although the helical region in p9 is longer (22 residues) than that of p6 (12 residues) under the same conditions. In each case the molecules are highly flexible and, unlike most structured proteins, must be considered as a dynamic equilibrium of many different conformers that have the overall propensity for secondary structure in the regions depicted in Fig. 8. Nevertheless, in its most structured form, the p6 molecule adopts a helix-turn-helix conformation in its C-terminal region whereas p9 assumes a single continuous helical conformation. The charge distribution within p6 and p9 is also distinctly different as the helix of p9 contains more charged residues than p6 (Fig. 8). Such differences in this helical region will be important for specific interactions with host cell factors (see below).


Solution structure of the equine infectious anemia virus p9 protein: a rationalization of its different ALIX binding requirements compared to the analogous HIV-p6 protein.

Sharma A, Bruns K, Röder R, Henklein P, Votteler J, Wray V, Schubert U - BMC Struct. Biol. (2009)

Schematic comparison of the Tsg101- and ALIX-binding domains of p6 and p9 in relation to the experimentally determined secondary structures in 50% TFE.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2803184&req=5

Figure 8: Schematic comparison of the Tsg101- and ALIX-binding domains of p6 and p9 in relation to the experimentally determined secondary structures in 50% TFE.
Mentions: In their most structured states both molecules possess stable secondary structure although neither molecule possesses a stable tertiary structure. In a hydrophobic environment at low pH, both adopt helical secondary structure in their C-termini, although the helical region in p9 is longer (22 residues) than that of p6 (12 residues) under the same conditions. In each case the molecules are highly flexible and, unlike most structured proteins, must be considered as a dynamic equilibrium of many different conformers that have the overall propensity for secondary structure in the regions depicted in Fig. 8. Nevertheless, in its most structured form, the p6 molecule adopts a helix-turn-helix conformation in its C-terminal region whereas p9 assumes a single continuous helical conformation. The charge distribution within p6 and p9 is also distinctly different as the helix of p9 contains more charged residues than p6 (Fig. 8). Such differences in this helical region will be important for specific interactions with host cell factors (see below).

Bottom Line: The structural elements identified for p9 differ substantially from that of the functional homologous HIV-1 p6 protein.However, p6 contains an additional PTAP L-domain that promotes HIV-1 release by binding to the tumor susceptibility gene 101 (Tsg101).The notion that structures found in p9 differ form that of p6 further support the idea that different mechanisms regulate binding of ALIX to primary versus secondary L-domains types.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Structural Biology, Helmholtz Centre for Infection Research, D-38124 Braunschweig, Germany. alok.sharma@gmail.com

ABSTRACT

Background: The equine infection anemia virus (EIAV) p9 Gag protein contains the late (L-) domain required for efficient virus release of nascent virions from the cell membrane of infected cell.

Results: In the present study the p9 protein and N- and C-terminal fragments (residues 1-21 and 22-51, respectively) were chemically synthesized and used for structural analyses. Circular dichroism and 1H-NMR spectroscopy provide the first molecular insight into the secondary structure and folding of this 51-amino acid protein under different solution conditions. Qualitative 1H-chemical shift and NOE data indicate that in a pure aqueous environment p9 favors an unstructured state. In its most structured state under hydrophobic conditions, p9 adopts a stable helical structure within the C-terminus. Quantitative NOE data further revealed that this alpha-helix extends from Ser-27 to Ser-48, while the N-terminal residues remain unstructured. The structural elements identified for p9 differ substantially from that of the functional homologous HIV-1 p6 protein.

Conclusions: These structural differences are discussed in the context of the different types of L-domains regulating distinct cellular pathways in virus budding. EIAV p9 mediates virus release by recruiting the ALG2-interacting protein X (ALIX) via the YPDL-motif to the site of virus budding, the counterpart of the YPXnL-motif found in p6. However, p6 contains an additional PTAP L-domain that promotes HIV-1 release by binding to the tumor susceptibility gene 101 (Tsg101). The notion that structures found in p9 differ form that of p6 further support the idea that different mechanisms regulate binding of ALIX to primary versus secondary L-domains types.

Show MeSH
Related in: MedlinePlus