EQUINE INFECTIOUS-ANEMIA VIRUS TAT IS A PREDOMINANTLY HELICAL PROTEIN

Nuclear magnetic resonance (NMR) spectroscopy revealed features of the secondary structure of the equine infectious anemia virus (EIAV) Tat protein in solution. We could show that this protein, which is require d in the replication cycle of lentiviruses, forms a predominantly heli cal structure in trifluoroethanol/water (40% by vol.) solution. In par ticular, the basic RNA-binding region and the adjacent core domain, wh ich are highly conserved among lentiviral Tat proteins, show helix-typ e secondary structure under these conditions. Our observations, in con cert with recent biochemical data from other laboratories, suggest tha t the core sequence region and the basic sequence region form interdep endent structural domains, both possibly necessary for correct RNA bin ding.