PDBsum entry 1kpp

Cell cycle

PDB id: 1kpp

Contents

Protein chain

144 a.a. *

* Residue conservation analysis

References listed in PDB file

Key reference

Title

Structure and functional interactions of the tsg101 uev domain.

Authors

O.Pornillos, S.L.Alam, R.L.Rich, D.G.Myszka, D.R.Davis, W.I.Sundquist.

Ref.

EMBO J, 2002, 21, 2397-2406. [DOI no: 10.1093/emboj/21.10.2397]

PubMed id

12006492

Abstract

Human Tsg101 plays key roles in HIV budding and in cellular vacuolar protein sorting (VPS). In performing these functions, Tsg101 binds both ubiquitin (Ub) and the PTAP tetrapeptide 'late domain' motif located within the viral Gag protein. These interactions are mediated by the N-terminal domain of Tsg101, which belongs to the catalytically inactive ubiquitin E2 variant (UEV) family. We now report the structure of Tsg101 UEV and chemical shift mapping of the Ub and PTAP binding sites. Tsg101 UEV resembles canonical E2 ubiquitin conjugating enzymes, but has an additional N-terminal helix, an extended beta-hairpin that links strands 1 and 2, and lacks the two C-terminal helices normally found in E2 enzymes. PTAP-containing peptides bind in a hydrophobic cleft exposed by the absence of the C-terminal helices, whereas ubiquitin binds in a novel site surrounding the beta-hairpin. These studies provide a structural framework for understanding how Tsg101 mediates the protein-protein interactions required for HIV budding and VPS.

Figure 3.
Figure 3 Chemical shift mapping of the PTAP binding site on Tsg101 UEV. (A) Overlay of the ^1H/^15N-HSQC spectra of Tsg101 UEV in the absence (gray) or presence of the 1.0 molar equivalent of PTAP peptide (red). The lower panels show an expansion of the boxed region with an additional titration point indicating that the Tsg101 UEV/PTAP complex is in slow exchange. (B) Biosensor binding of Tsg101 UEV to immobilized full-length p6 (upper left panel and closed circles) and PTAP peptide to immobilized Tsg101 UEV (lower left panel and open circles). The near superimposition of the two curves demonstrates that Tsg101 UEV binds p6 and the PTAP peptide with the same affinity.

Figure 6.
Figure 6 Comparison of the ubiquitin binding site (blue residues) on Tsg101 UEV (yellow) with models for the two distinct ubiquitin binding sites (purple) on the Ubc13/Mms2 heterodimer (gray) (VanDemark et al., 2001). To create the figure, Tsg101 UEV was superimposed on either the Ubc13 E2 (A) or the Mms2 UEV (B) subunits of the Ubc13/Mms2 heterodimer. The figure illustrates the fact that the Ub binding surface on Tsg101 is distinct from previously characterized Ub binding sites on either E2 or UEV domains, but does roughly correspond to the Mms2 binding site on Ubc13.

The above figures are reprinted from an Open Access publication published by Macmillan Publishers Ltd: EMBO J (2002, 21, 2397-2406) copyright 2002.