Viruses resemble in many aspects functional moduls of the cell. In infected cells a limited set of macromolecules assembles in a hierarchical order to a functional unit, the virus particle, which then buds from the plasma membrane and disassembles upon entry into a new cell. Influenza viruses, the object of our project, consist of a membrane with the glycoproteins hemagglutinin (HA) and neuramindase (NA) inserted and of the viral core with eight ribonucleoparticles (vRNPs), each containing a viral gene. Located between both components is the matrix protein (M1), which organizes virus assembly and, together with HA and NA as well as the viral proton-channel M2, executes budding.
In the first period we have studied protein-lipid interactions and the relevance of lipid domains for local recruitment of HA and M1 to cellular membranes as an initial step of virus assembly. In the second period we will study: (i) the relevance of protein-protein interactions for local enrichment of viral proteins and formation of the assembly site of influenza virus. In particular, we will investigate the proposed interactions of M1 with itself (oligomerisation) and with the cytoplasmic tails of M2, HA and NA and aim at identifying the determinants that select the viral assembly site in polarized cells. (ii) the underlying mechanism of vRNP recruitment to the assembly site of influenza virus. (iii) the role of HA, NA, M1 and M2 and their interactions for generation of membrane curvature required for budding of virus particles and subsequent membrane scission.
We will use recently developed tools to identify lipid domains of submicroscopic size, biophysical methods to analyze interaction of proteins with these domains and also reverse genetics to generate mutant influenza virus to test our conclusion with the complete viral module.

http://www.sfb740.de/subprojects/project-area-c/subproject-c3