D. Willbold et al., SEQUENCE-SPECIFIC RESONANCE ASSIGNMENTS OF THE H-1-NMR SPECTRA OF A SYNTHETIC, BIOLOGICALLY-ACTIVE EIAV TAT PROTEIN, Biochemistry, 32(33), 1993, pp. 8439-8445
The equine infectious anemia virus (EIAV) trans-activating (Tat) prote
in is a close homologue of the human immunodeficiency virus (HIV) Tat
protein. Both of these proteins bind to an RNA trans-activation respon
sive element (TAR). We synthesized chemically a protein with the seque
nce of the 75 amino acid Tat protein from EIAV. The chemically synthes
ized protein was shown to be biologically active. Circular dichroism (
CD) and H-1 nuclear magnetic resonance (NMR) spectroscopy were used to
structurally characterize the synthetic protein. We obtained nearly c
omplete resonance assignments in the 2D-NMR spectra of the protein at
PH 3.0. There is at least some evidence from the experimental data tha
t the basic TAR binding domain of the synthetic protein has a tendency
to form a helix, but our experiments also indicate that the protein p
robably does not have an overall stable tertiary structure in aqueous
solution at this pH. CD spectroscopy suggested that the protein adopts
a more stable, predominantly alpha-helical structure in a trifluoroet
hanol/water solution.