Keywords:High-Speed Atomic Force Microscopy (HS-AFM), virus infectivity factor (Vif), singlestranded DNA (ssDNA), double-stranded DNA (dsDNA),the human APOBEC3 family of cytidine deaminases (APOBEC3) proteins, Vif-Elongin-C, Elongin-B-CBF-β complex (VCBC), human immunodeficiency virus (HIV), acquired immune deficiency syndrome (AIDS).
AbstractViral infectivity factor (Vif) is a protein that is essential for the replication of the HIV-1 virus. The key function of Vif is to disrupt the antiviral activity of APOBEC3 proteins, which mutate viral nucleic acids. Inside the cell, Vif binds to the host cell proteins Elongin-C, Elongin-B, and CBF-β, forming a fourprotein complex called VCBC. The structure of VCBC in complex with the Cullin5 (Cul5) protein has been solved by X-ray crystallography, and recently, using molecular dynamic (MD) simulations, the dynamics of VCBC and VCBC-Cul5 complexes were characterized. Here, we applied time-lapse highspeed atomic force microscopy (HS-AFM) to visualize the conformational changes of the VCBC complex. We determined the three most favorable conformations of the VCBC complex, which we identified as triangle, dumbbell, and globular structures. In addition, we characterized the dynamics of each of these structures. While our data show a very dynamic behavior for all these structures, we found the triangle and dumbbell structures to be the most dynamic. These findings provide insight into the structure and dynamics of the VCBC complex and support further research into the improvement of HIV treatment, as Vif is essential for virus survival in the cell.