C-terminal residues of mature human T-lymphotropic virus type 1 protease are critical for dimerization and catalytic activity

Biochem J. 2008 Dec 15;416(3):357-64. doi: 10.1042/BJ20071132.

Abstract

HTLV-1 [HTLV (human T-cell lymphotrophic virus) type 1] is associated with a number of human diseases. HTLV-1 protease is essential for virus replication, and similarly to HIV-1 protease, it is a potential target for chemotherapy. The primary sequence of HTLV-1 protease is substantially longer compared with that of HIV-1 protease, and the role of the ten C-terminal residues is controversial. We have expressed C-terminally-truncated forms of HTLV-1 protease with and without N-terminal His tags. Removal of five of the C-terminal residues caused a 4-40-fold decrease in specificity constants, whereas the removal of an additional five C-terminal residues rendered the protease completely inactive. The addition of the N-terminal His tag dramatically decreased the activity of HTLV-1 protease forms. Pull-down experiments carried out with His-tagged forms, gel-filtration experiments and dimerization assays provided the first unequivocal experimental results for the role of the C-terminal residues in dimerization of the enzyme. There is a hydrophobic tunnel on the surface of HTLV-1 protease close to the C-terminal ends that is absent in the HIV-1 protease. This hydrophobic tunnel can accommodate the extra C-terminal residues of HTLV-1 protease, which was predicted to stabilize the dimer of the full-length enzyme and provides an alternative target site for protease inhibition.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Aspartic Acid Endopeptidases / chemistry*
  • Aspartic Acid Endopeptidases / genetics
  • Aspartic Acid Endopeptidases / metabolism*
  • Dimerization
  • Human T-lymphotropic virus 1 / enzymology*
  • Humans
  • Isoenzymes / chemistry
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Structure, Quaternary*
  • Sequence Alignment
  • Structure-Activity Relationship

Substances

  • Isoenzymes
  • Aspartic Acid Endopeptidases
  • HTLV-1 protease