Activating region of HIV-1 Tat protein: vacuum UV circular dichroism and energy minimization.
Tat protein is a trans-acting transcriptional activator of the human immunodeficiency virus type 1 and is essential for viral transcription. By homology with other transcriptional activators, Tat is expected to possess a nucleic acid binding region and a separate adjacent activating region. In order to localize the activating region of Tat, we have synthesized the sequences 2-23 and 38-60 of the protein. These two peptides contain the two candidates for the activating regions proposed from mutation experiments in previous studies: sequence 1-13 and sequence 38-45. The argument advanced to justify the location of the activating region within the sequence 1-13 was the periodicity of acidic, polar, and hydrophobic residues consistent with that of an amphipathic alpha-helix, similar to the activating region of many eukaryotic transcriptional activators. We have monitored by vacuum UV circular dichroism the ability of each peptide to adopt an alpha-helical conformation under conditions that strongly favor the formation of secondary structures. Only peptide 38-60 adopts an alpha-helical conformation in these conditions, in keeping with Chou-Fasman prediction. Energy minimization and molecular dynamics were carried out for several possible conformations of sequences 1-14 and 38-60. Our results indicate that only the sequence 38-45 is able to form an alpha-helix with amphipathic characteristics.
Loret
E P
EP
Department of Biochemistry and Biophysics, Oregon State University, Corvallis 97331-6503.
Vives
E
E
Ho
P S
PS
Rochat
H
H
Van Rietschoten
J
J
Johnson
W C
WC
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D003198:Computer Simulation; D015696:Gene Products, tat / Q000138:chemical synthesis / Q000737:chemistry*; D015497:HIV-1 / Q000235:genetics*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D010455:Peptides; D054322:tat Gene Products, Human Immunodeficiency Virus