Predicted Structure and Functions of the Prototypic Alphaherpesvirus Herpes Simplex Virus Type-1 UL37 Tegument Protein

Abstract

The alphaherpesvirus UL37 tegument protein is a highly conserved, multi-functional protein. Mutagenesis analysis delineated the UL37 domains necessary for retrograde transport and viral replication. Specifically, the amino-terminal 480 amino acids are dispensable for virus replication in epithelial cell culture, but it is unknown whether this amino-terminal deletion affects UL37 structure and intracellular transport in epithelial cells and neurons. To investigate the structure and function of UL37, we utilized multiple computational approaches to predict and characterize the secondary and tertiary structure and other functional features. The structure of HSV-1 UL37 and Δ481N were deduced using publicly available predictive algorithms. The predicted model of HSV-1 UL37 is a stable, multi-functional, globular monomer, rich in alpha helices, with unfolded regions within the linker and the C-tail domains. The highly flexible C-tail contains predicted binding sites to the dynein intermediate chain, as well as DNA and RNA. Predicted interactions with the cytoplasmic surface of the lipid membrane suggest UL37 is a peripheral membrane protein. The Δ481N truncation did not alter the predicted structure of the UL37 C-terminus protein and its predicted interaction with dynein. We validated these models by examining the replication kinetics and transport of the Δ481N virus toward the nuclei of infected epithelial and neuronal cells. The Δ481N virus had substantial defects in virus spread; however, it exhibited no apparent defects in virus entry and intracellular transport. Using computational analyses, we identified several key features of UL37, particularly the flexible unstructured tail; we then demonstrated that the UL37 C-terminus alone is sufficient to effectively transport the virus towards the nucleus of infected epithelial and neuronal cells.

Inactivation of the UL37 Deamidase Enhances Virus Replication and Spread of the HSV-1(VC2) Oncolytic Vaccine Strain and Secretion of GM-CSF

“…HSV-1 UL37 tertiary structure was modeled using AlphaFold2 as previously described [ 38 ]. The C819 location was identified in the center of an elongated alpha helix within the C-terminal half ( Figure 5 A).…”

Using AlphaFold Predictions in Viral Research

“…AlphaFold is widely used in research on other eukaryotic viruses, including monkeypox virus (MPXV) [ 31 , 32 , 33 , 34 ], herpes simplex virus [ 35 , 36 ], hepatitis E virus (HEV) [ 37 ] and other viral pathogens of humans and economically significant animals and plants [ 38 , 39 , 40 , 41 , 42 , 43 ]. Monkeypox virus (MPXV) represents a new serious threat to human health.…”

“…Specific protein–protein interactions have been shown to be essential for lipid metabolism [ 35 ]. The use of AlphaFold has also shown that another HSV-1 protein, the tegument protein UL37, interacts with the cytoplasmic surface of the lipid membrane, suggesting that UL37 can be a peripheral membrane protein [ 36 ]. AlphaFold predictions have suggested the domain organisation of UL37, and assisted experimental studies and molecular dynamics simulation have clarified the structural features and molecular mechanisms of UL37 interactions.…”