A photography of proteinsamples in a SDS-Gel.
Understanding the very specific interaction of viral proteins with cellular binding partners represents an essential prerequisite for deciphering the patho-mechanism of viral infection, and this knowledge in turn is essential for the design of strategies for anti-viral treatment and vaccination. Over a number of years the research group "Biophysical Analysis" has had an exceptionally successful interdisciplinary collaboration with Porfessor U. Schubert’s group (now at the Institute of Clinical and Molecular Virology, University of Erlangen) on the structure and function of a number of HIV-1 specific accessory proteins and most recently on a novel influenza A virus protein, PB1-F2.
Their early work on HIV-1 virus protein U (Vpu) led to the proposal of a novel model of the membrane bound structure of the protein which further provided a rational of two functional aspects of Vpu, namely its regulation of the degradation of CD4 and its ion-channel function.
In an extension of this work the scientists studied the molecular structure and function of the HIV-1 regulatory protein R, Vpr, which plays a major role in the multifaceted picture of pathogenesis related to HIV and SIV infections. The discovery of an unusually high cis-isomer content of conserved proline residues in the structural elucidation of the N-terminus of Vpr led to the unprecedented finding of a critical functional interaction of Vpr with an ubiquitous host protein, cyclophilin A (CypA). This protein is important for the de novo synthesis of Vpr and regulates the Vpr mediated cell cycle arrest in HIV-1 infected T cells.
Among known lentiviruses, the 52 amino acid HIV-1 p6 protein is by far the smallest protein. Although p6 fulfils major functions in the formation of infectious viruses and represents a docking site for several cellular and viral binding factors, the molecular structure of this virus protein, which can be relatively easy synthesized by standard solid phase peptide synthesis, has not been properly defined. Recently, the solution structure of the UEV domain of Tsg101 was resolved in complex with the peptide binding site of HIV-1 p6, embodied as the nine residue L-domain containing peptide PEPTAPPEE. The L-domain, which itself is believed to reside within an unstructured region of p6, connects to a cavernous pocket of the UEV domain of Tsg101 that bears a resemblance to the binding sites of SH3 and WW domains.
Most recently the researchers have synthesized and characterized an 87 amino acid, pro-apoptotic influenza A virus accessory protein PB1-F2, first reported in 2001, which shows striking similarity to Vpr. This protein originates from an alternative reading frame in the PB1 polmerase gene and is encoded in most known human IAV isolates. Currently they are engaged in the study of the structural and functional characterization of this novel protein.
In their recent work they re-explored the high resolution structure and folding of synthetic p6 under various solution conditions using a combination of CD and NMR spectroscopy. In its most structured state, p6 adopts a helix-flexible-helix structure: a short helix-1 (residues 14-18) is connected to a pronounced helix-2 (residues 33-44) by a flexible hinge region. Synthetic peptides were then used to show that helix-2 of p6, which comprises the LXXLF binding motif for Vpr, specifically interacts with Vpr.
