Molecular recognition of ligands by native viruses and virus-like particles as studied by NMR experiments

Viral entry into host cells is a process that in the majority of cases is not understoodin its molecular details. The first step of viral entry is the recognition of cellular receptorson host cells by viruses, and although X-ray crystallography had yielded some spectacular resultsin individual cases, in general there is little data available to unravel the principles of virus-ligandrecognition at atomic resolution. Therefore, new techniques that uncover the molecular details ofthese recognition processes are needed. The investigation of virus-ligand interactions usingligand-based NMR techniques is an emerging field with the potential to substantially contribute toa deeper understanding of the molecular aspects of viral entry into host cells. Here, we givean overview that covers some of the systems studied so far. This comprises native viruses as wellas virus-like particles (VLPs). We will not address studies that have been performed with individualproteins that are not in a native environment. It turns out that STD NMR in particular has a greatpotential to shine light on the viral entry process as this technique requires only very moderateamounts of viruses or VLPs and corresponding ligands. As a further advantage, this approachis also applicable to ligands that bind to viruses with medium to low affinity. Therefore, STD NMRis extremely well suited for development of antiviral entry inhibitors utilizing fragment-based approacheswith low molecular weight compounds.