Folding and dynamics of membrane proteins and HIV-1 Tat

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All cells and their organelles are surrounded by a membrane. Protein channels and receptors that are embedded in membranes precisely control the flow of nutrients, waste products, energy, and even information into and out of cells and organelles. Membrane proteins comprise 20-30% of all cellular protein and it is likely that 50% of all future targets for drug development will be membrane proteins, yet only 1.6% of all known protein structures belong to membrane proteins. Knowledge of the molecular structures and dynamics of membrane proteins is essential for understanding the functioning of many basic processes in cell biology and medicine. Our long-term goal is to develop methods to overcome the many difficulties in membrane protein structure and dynamics determination. Recently, we have made progress in studying the structure and folding of a bacterial membrane protein, the glycerol facilitator. We propose to continue this work by developing our system for investigation by Nuclear Magnetic Resonance (NMR) spectroscopy, a method analogous to Magnetic Resonance Imaging.  Once developed, we will apply our methods to the study of other membrane receptors such as the temperature-sensitive receptors that mediate the senses of hot and cold. It is thought that their function is determined by changes in their structures and NMR is particularly well suited to the measurement of protein dynamics. We will also continue our work on the fungal antibiotic peptide alamethicin that is a model membrane protein. HIV-1 Transactivator of transcription (Tat) is a small Human Immunodeficiency Virus protein that is a key player in the regulation of HIV-1 replication, HIV-1 latency, immune suppression, and AIDS-related dementia. We have recently prepared Tat protein and studied its structure and dynamics by NMR. We have found that the protein is natively unfolded which helps to explain why it can interact with such a wide variety of proteins. We propose to study the structure of Tat bound to another protein named calmodulin that is found in most cells. Understanding the molecular basis of Tat binding will contribute to a better understanding of its role in HIV-1 infection and may provide the basis of improving therapies.