MARGARET C KIELIAN

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..Inhibition of the fusion protein refolding reaction confirms its importance in fusion and suggests new antiviral strategies for these medically important viruses...

..This review will focus in particular on the properties of the more recently described class II proteins...

..We discuss results using truncated proteins to dissect the fusion reaction, and future research directions including the development of antiviral therapies against these medically important viruses...

..These novel inhibitors of the class II fusion proteins show cross-inhibition within the virus genus and suggest that the domain III-core trimer interaction can serve as a new target for the development of antiviral reagents...

..Truncated DV E proteins thus reconstitute hairpin formation and define properties of key domain interactions during DV fusion...

..Thus, the membrane insertion of the E1 fusion peptide is regulated by additional low-pH-dependent steps after exposure, perhaps involving an E1-cholesterol interaction...

..While there are extensive contacts between E1 subunits in the homotrimer, the D188K mutant identifies an important "hot spot" for protein-protein interactions within the core trimer...

..SFV E1 is the first virus fusion protein demonstrated to directly bind cholesterol. Taken together, our results reveal important functional differences conferred by the cholesterol-binding properties of class II fusion proteins...

..Together the revertants reveal specific and interconnected aspects of the fusion protein refolding reaction...

..Our data suggest that E1 hairpin formation occurs by the sequential packing of domain III and the stem onto the trimer core and indicate a tight correlation between stem packing and membrane merger...

..Even in the absence of DIII, DI/II trimers interacted to form hexagonal lattices and to cause membrane deformation and tubulation. These studies identify a prefusion intermediate in class II membrane fusion...

..Our results indicate that the E1 ij loop and the conserved H230 residue play a critical role in alphavirus-membrane fusion and suggest the presence of a previously undescribed late intermediate in the fusion reaction...

..Together, these results and the location of H3 suggest that this residue acts to regulate the low-pH-dependent refolding of E1 during membrane fusion...

..However, the in vivo infectivity of mutant L was more strongly inhibited than that of wt/p62, due to additional effects of the mutation on virus-cell binding...

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..These differences raise many interesting questions about virus assembly and fusion activity...

..Our data allow the visualization of a viral fusion protein inserted in its target membrane and demonstrate that insertion is a cooperative process, resulting in rings composed of five to six homotrimers...

..Determination of the structure will provide our first high-resolution views of both the low-pH-induced trimeric conformation and the target membrane-interacting region of the alphavirus fusion protein...

..TM domain glycine residues thus are not required for efficient SFV fusion or assembly but can cause subtle effects on the properties of membrane fusion...

..Our data suggest that there is an important p62/E1 dimer interaction site identified by an E2 R250G mutation and that this interaction is maintained after processing to the mature E2 protein...

..Thus, the srf-4 and srf-5 mutations identify novel regions of E1 that are distinct from the fusion peptide and srf-3 region and modulate the requirements for both sphingolipid and cholesterol in virus-membrane fusion...

..Together, our data support a model in which a ring of three salt bridges formed by D188 and K176 stabilize the core trimer, a key intermediate of the alphavirus fusion protein...

..In contrast, SFV budding was independent of both ubiquitin and the activity of VPS4, perhaps reflecting the important role of the highly organized envelope protein lattice during alphavirus budding...

..Sequence analysis of the pci mutants identified mutations primarily on the E2 protein, and suggested sites important in the interaction of p62 with E1 and the regulation of fusion...

..Together, our data identify two separate regions of the SFV E1 ectodomain, one responsible for target membrane association and one necessary for trimer interactions...

..The lack of a specific stem sequence requirement during SFV fusion suggests that the interaction of domain III with the trimer core can provide sufficient driving force to mediate membrane merger...

..Ph. D. graduates develop the expertise, knowledge and critical abilities essential for a successful career in science. ..

..This application focuses on developing new antiviral strategies for the flaviviruses and alphaviruses, based on blocking the activity of the proteins involved in the initial entry of the virus into the cell. ..