HIV-1 gp41 by N-domain binds the potential receptor protein P45

Bridging the past and the future of virology: surface plasmon resonance as a powerful tool to investigate virus/host interactions

Despite decades of antiviral drug research and development, viruses still remain a top global healthcare problem. Compared to eukaryotic cells, viruses are composed by a limited numbers of proteins that, nevertheless, set up multiple interactions with cellular components, allowing the virus to take control of the infected cell. Each virus/host interaction can be considered as a therapeutical target for new antiviral drugs but, unfortunately, the systematic study of a so huge number of interactions is time-consuming and expensive, calling for models overcoming these drawbacks. Surface plasmon resonance (SPR) is a label-free optical technique to study biomolecular interactions in real time by detecting reflected light from a prism-gold film interface. Launched 20 years ago, SPR has become a nearly irreplaceable technology for the study of biomolecular interactions. Accordingly, SPR is increasingly used in the field of virology, spanning from the study of biological interactions to the identification of putative antiviral drugs. From the literature available, SPR emerges as an ideal link between conventional biological experimentation and system biology studies functional to the identification of highly connected viral or host proteins that act as nodal points in virus life cycle and thus considerable as therapeutical targets for the development of innovative antiviral strategies.

Bioanalytical interaction studies executed by preincubation affinity capillary electrophoresis

The versatility of CE is beneficial for the study of many types of molecular interactions, because different experimental designs can be made to suit the characteristics of a particular interaction. A very versatile starting point is the preequilibration type of affinity CE that has been used extensively for characterizing biomolecular interactions in the last 15 years. We review this field here and include a comprehensive overview of the existing preincubation ACE modes including their advantages and limitations as well as the methodological developments and applications within the bioanalytical field.

Spying on HIV with SPR

The application of surface plasmon resonance (SPR)-based optical biosensors has contributed extensively to our understanding of functional aspects of HIV. SPR biosensors allow the analysis of real-time interactions of any biomolecule, be it protein, nucleic acid, lipid, carbohydrate or small molecule, without the need for intrinsic or extrinsic probes. As such, the technology has been used to analyze molecular interactions associated with every aspect of the viral life cycle, from basic studies of binding events occurring during docking, replication, budding and maturation to applied research related to vaccine and inhibitory drug development. Along the way, SPR biosensors have provided a unique and detailed view into the inner workings of HIV.

Characterization of interaction between C-domain on HIV-1 gp41 and the putative receptor protein p62

Based on the fact that the binding of HIV-1 gp41 to the putative cellular receptor protein p62 could be inhibited by the C-domain peptide of gp41, we wanted to confirm the interaction of the C-domain with p62 and to characterize the receptor-binding site on the C-domain. We attempted to isolate the putative receptor protein p62 from cell lysates of the human B cell line Raji by affinity chromatography using sepharose-columns which were conjugated with three different peptides of the C-domain respectively. A protein of 62 kDa was isolated by peptide (NP2)-sepharose-column, while none of the proteins was identified in eluates of the other two overlapped peptides of C-domain, indicating that HIV-1 gp41 by the region aa635-664 of C-domain binds to the putative receptor protein p62. Besides, CD spectroscopy analysis revealed that only a NP2 peptide could induce significant conformational change of P62. In addition, the interaction between P62 and three peptides of the C-domain was characterized by the surface plasma resonance (SPR) measurement. It was indicated that only the NP2 peptide significantly inhibited the interaction between rsgp41 and the putative receptor P62, confirming that the protein p62 may serve as a potential receptor for gp41 binding, and the peptide NP2 contains an integrate binding site for gp41 binding to p62.

Recent advances in affinity capillary electrophoresis

Use of the specificity of (bio)interactions can effectively overcome the selectivity limitation faced in capillary electrophoresis (CE), and the resulting technique usually is referred to as affinity capillary electrophoresis (ACE). Despite the high selectivity of ACE, several important problems still need to be addressed. A major issue in all CE separations, including ACE, is the concentration detection limit. Using UV detection, this is usually in the order of 10(-6) M whereas laser-induced fluorescence (LIF) detection can provide detection limits down to the sub-10(-10) M range. However, a marked disadvantage of LIF is that labeling of the analytes is usually required, which might change the interaction behavior of the solutes under investigation. Additionally, labeling reactions at sub-10(-10) M concentration levels are certainly not trivial and often difficult to perform quantitatively. Alternative and universal detection approaches, particularly mass spectrometric (MS) detection, look very promising but (A) CE-MS techniques are still far from routine application. Important future progress in sensitive detection strategies is likely to increase the use of ACE in the future.