Molecular Biophysics
Structure and Glycan Binding of a New Cyanovirin-N Homolog
The HIV-1 envelope glycoprotein gp120 is heavily glycosylated and bears numerous high mannose sugars. These sugars can serve as targets for HIV-inactivating compounds, such as antibodies and lectins, which bind to the glycans and interfere with viral entry into the target cell. We determined the 1.6 Å x-ray structure of Cyt-CVNH, a recently identified lectin from the cyanobacterium Cyanothece7424, and elucidated its glycan specificity by NMR. The Cyt-CVNH structure and glycan recognition profile are similar to those of other CVNH proteins, with each domain specifically binding to Manα(1–2)Manα units on the D1 and D3 arms of high mannose glycans.Structural Basis of Clade-specific Engagement of SAMHD1 (Sterile α Motif and Histidine/Aspartate-containing Protein 1) Restriction Factors by Lentiviral Viral Protein X (Vpx) Virulence Factors
Background Lentiviral Vpx binding to primate SAMHD1 is under positive selection. Results Different Vpx protein variants interact with the N-terminal domain or the C-terminal tail of SAMHD1 in ubiquitin-ligase-substrate receptor complexes in a unique fashion. Conclusion Vpx antagonizes SAMHD1 by recruiting it via two separate regions for proteasomal degradation. Significance Our findings shed light on how lentivirus virulence factors intersect with host innate immunity.
