Molecular determinants for recognition of divergent SAMHD1 proteins by the lentiviral accessory protein Vpx.
Bottom Line: Comparison with Vpx from SIV that infects sooty mangabeys (SIVsmm) complexed with SAMHD1-DCAF1 identifies molecular determinants directing Vpx lineages to N- or C-terminal SAMHD1 sequences.Inspection of the Vpx-DCAF1 interface also reveals conservation of Vpx with the evolutionally related HIV-1/SIV accessory protein Vpr.These data suggest a unified model for how Vpx and Vpr exploit DCAF1 to promote viral replication.
Affiliation: Division of Molecular Structure, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK.Show MeSH
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Mentions: In the complex, the N-terminal NLS region (residues 1–22) of SAMHD1mnd comprises an extended chain that binds to the edge of DCAF1 in an interface that buries 500 Å2 of solvent accessible surface (Figure 4A; Table S1B). Here, residues D5, D7, and Q8 make extensive sidechain and mainchain hydrogen bonds to residues in the interspersing loops of DCAF1 WD40 repeat-1. In addition, SAMHD1 residues R12 and R14, which are part of the SAMHD1 NLS (Brandariz-Nuñez et al., 2012; Hofmann et al., 2012), make salt bridges to E1091 and D1092 in the DCAF1 acidic loop. The ternary interaction is completed by a 750 Å2 SAMHD1mnd-SIVmnd-2 Vpx interface that includes multiple interactions with Vpx residues from the N-terminal arm, α1, and the α2-α3 loop (Figure 4B; Table S1C). One feature of this interface is a “trapped” region where the Vpx N-terminal arm wraps over SAMHD1 packing it against DCAF1. Within the trapped region, the main chains of SAMHD1 and Vpx interact through hydrogen bonding between E10, G13, and E14 of Vpx and Q2 and S10 of SAMHD1. In addition, the main chain of Vpx G13, and E14 also make interactions with the SAMHD1 D7 and S10 side chains. C-terminal to the trapped region there are further interactions where Vpx V15, L17, and W20 create a hydrophobic pocket at the N terminus of α1 that SAMHD1 P9 inserts into. Additionally, SAMHD1 NLS residue R12 makes a hydrogen bond to Vpx Y65, SAMHD1 F15 stacks with Vpx R58, and SAMHD1 R20 makes an electrostatic interaction with Vpx D54 (Figure 4B).
Affiliation: Division of Molecular Structure, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK.