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Tyrosine hydroxylase and tryptophan hydroxylase do not form heterotetramers

Authors
  • Mockus, Susan M.1
  • Yohrling, George J.2
  • Vrana, Kent E.2
  • 1 Wake Forest University School of Medicine, Program in Neuroscience, Winston-Salem, NC, 27157-1083 , Winston-Salem
  • 2 Wake Forest University School of Medicine, Department of Physiology and Pharmacology, Winston-Salem, NC, 27157-1083 , Winston-Salem
Type
Published Article
Journal
Journal of Molecular Neuroscience
Publisher
Springer-Verlag
Publication Date
Feb 01, 1998
Volume
10
Issue
1
Pages
45–51
Identifiers
DOI: 10.1007/BF02737084
Source
Springer Nature
Keywords
License
Yellow

Abstract

Tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH) both contain a C-terminal tetramerization domain composed of a leucine heptad repeat embedded within a 4,3-hydrophobic repeat. Previous mutagenesis experiments and X-ray crystallographic studies have demonstrated that these repeats are required for tetramer assembly of the hydroxylase enzymes via coiled-coil interactions. The specificity of these particular C-terminal intersubunit binding motifs was investigated by determining if TH and TPH can form heterotetramers when coexpressed in bacteria. Bacterial cells were cotransformed with TH and TPH expression plasmids under kanamycin and ampicillin selection, respectively. Immunoprecipitation of induced bacterial supernatants with a TPH monoclonal antibody demonstrated that, unlike the human TH isoforms, TH and TPH do not form heterotetramers. The data suggest that specificity of oligomerization of the aromatic amino acid hydroxylases may be partially determined by polar amino acids interspersed within the coiled-coil. This finding should be influential in the development of eukaryotic expression systems and ultimately in gene therapy approaches.

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