Abstract
Tryptophan hydroxylase (TPH) catalyzes the rate-limiting step in the biosynthesis of serotonin. In the rabbit, TPH exists as a tetramer of four identical 51-kDa subunits comprised of 444 amino acids each. The enzyme consists of an amino-terminal regulatory domain and a carboxyl-terminal catalytic domain. Previous studies demonstrated that within the carboxyl-terminus of TPH, there resides an intersubunit binding domain (a leucine zipper) that is essential for tetramer formation. However, it is hypothesized that a 4,3-hydrophobic repeat identified within the regulatory domain of TPH (residues 21–41) may also be involved in macromolecular assembly. To test this hypothesis, a series of amino-terminal deletions (NΔ15, 30, 41, and 90) were created and assessed for macromolecular structure using size-exclusion chromatography. The amino-terminal deletion NΔ15, upstream from the 4,3-hydrophobic repeat, was capable of forming tetramers. However, when a portion of the 4,3-hydrophobic repeat was deleted (NΔ30), a heterogeneous elution pattern of tetramers, dimers, and monomers was observed. Complete removal of the 4,3-hydrophobic repeat (NΔ41) rendered the enzyme incapable of forming tetramers; a monomeric form predominated. In addition, a double-point mutation (V28R-L31R) was created in the hydrophobic region of the enzyme. The introduction of two arginines (R) at positions 28 and 31 respectively, in the helix disrupted the native tetrameric state of TPH. According to size-exclusion chromatography analysis, the double-point mutant (V28R-L31R) formed dimers of 127 kDa. Thus, it is concluded that there is information within the amino-terminus that is necessary for tetramer formation of TPH. This additional intersubunit binding domain in the amino-terminus is similar to that found in the carboxyl-terminus.
Similar content being viewed by others
Abbreviations
- HRP:
-
horseradish peroxidase
- NΔ:
-
amino-terminal deletion
- PAGE:
-
polyacrylamide gel electrophoresis
- PH:
-
phenylalanine hydroxylase
- SDS:
-
sodium dodecyl sulfate
- TH:
-
tyrosine hydroxylase
- TPH:
-
tryptophan hydroxylase
- GST:
-
glutathione-S-transferase
- dNTP:
-
deoxynucleoside triphosphate (mixed base)
References
Abate C. and Joh T. H. (1991) Limited proteolysis of rat brain tyrosine hydroxylase defines an N-terminal region required for regulation of cofactor binding and directing substrate specificity. J. Mol. Neurosci. 2, 203–215.
Abate C., Smith J. A., and Joh T. H. (1988) Characterization of the catalytic domain of bovine adrenal tyrosine hydroxylase. Biochem. Biophys. Res. Commun. 151, 1446–1453.
Beevers S. J., Knowles R. G., and Pogson C. I. (1983) A sensitive radiometric assay for tryptophan hydroxylase applicable to crude extracts. J. Neurochem. 40, 894–897.
Bonnefoy E., Ferrara P., Rohrer H., Gros F., and Thibault J. (1988) Role of the N-terminus of rat pheochromocytoma tyrosine hydroxylase in the regulation of the enzyme’s activity. J. Biochem. 174, 685–690.
Daubner S. C. and Piper M. M. (1995) Deletion mutants of tyrosine hydroxylase identify a region critical for heparin binding. Protein Sci. 4, 538–541.
Daubner S. C., Lohse D. L., and Fitzpatrick P. F. (1993) Expression and characterization of catalytic and regulatory domains of rat tyrosine hydroxylase. Protein Sci. 2, 1452–1460.
D’Sa C. M., Arthur R. E. Jr., Jennings I., Cotton R. G. H., and Kuhn D. M. (1996a) Tryptophan hydroxylase: Purification by affinity chromatography on calmodulin-sepharose. J. Neurosci. Methods 69, 149–153.
D’Sa C. M., Arthur R. E. Jr., and Kuhn D. M. (1996b) Expression and deletion mutagenesis of tryptophan hydroxylase fusion proteins: delineation of the enzyme catalytic core. J. Neurochem. 67, 917–926.
Goodwill K. E., Sabatier C., Marks C., Eaag R., Fitzpatrick P. F., and Stevens R. C. (1997) Crystal structure of tyrosine hydroxylase at 2.3Å and its implications for inherited neurodegenerative diseases. Nature Struct. Biol. 4, 578–585.
Grenett H. E., Ledley F. D., Reed L. L., and Woo S. L. C. (1987) Full-length cDNA for rabbit tryptophan hydroxylase: Functional domains and evolution of aromatic amino acid hydroxylases. Proc. Natl. Acad. Sci. USA 84, 5503–5534.
Grima B., Lamouroux A., Blanot F., Faucon Biguet N., and Mallet J. (1985) Complete coding sequence of rat tyrosine hydroxylase mRNA. Proc. Natl. Acad. Sci. USA 82, 617–621.
Hufton S. E., Jennings I. G., and Cotton R. G. H. (1995) Structure and function of the aromatic amino acid hydroxylases. Biochem. J. 311, 353–366.
Hufton S. E., Jennings I. G., and Cotton R. G. H. (1998) Structure/function analysis of the domains required for the multimerisation of phenylalanine hydroxylase. Biochim. Biophys. Acta 1382, 295–304.
Kiuchi K., Kiuchi K., Titani K., Fujita K., Suzuki K., and Nagatsu T. (1991) Limited proteolysis of tyrosine hydroxylase by Ca2+-activated neutral protease (calpain). Biochemistry 30, 10,416–10,419.
Knappskog P. M., Flatmark T., Aarden J. M., Haavik J., and Martinez A. (1996) Structure/function relationships in human phenylalanine hydroxylase. Eur. J. Biochem. 242, 813–821.
Kobe B., Jennings I. G., House C. M., Feil S. C., Michell B. J., Tiganis T., et al. (1997) Regulation and crystallization of phosphorylated and dephosphorylated forms of truncated dimeric phenylalanine hydroxylase. Protein Sci. 6, 1352–1357.
Kuhn D. M., Ruskin B., and Lovenberg W. (1980) Tryptophan hydroxylase: the role of oxygen, iron, and sulfhydryl groups as determinants of stability and catalytic activity. J. Biol. Chem. 255, 4137–4143.
Kumer S. C., Mockus S. M., Rucker P. J., and Vrana K. E. (1997) Amino terminal deletion analysis of tryptophan hydroxylase: PKA phosphorylation occus at serine-58. J. Neurochem. 69, 1738–1745.
Laemmli U. K. (1970) Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 227, 680–685.
Lohse D. L. and Fitzpatrick P. F. (1993) Identification of the intersubunit binding region in rat tyrosine hydroxylase. Biochem. Biophys. Res. Commun. 197, 1543–1548.
Mockus S. M. and Vrana K. E. (1998) Advances in the molecular characterization of tryptophan hydroxylase. J. Mol. Neurosci. 10, 163–179.
Mockus S. M., Kumer S. C., and Vrana K. E. (1997a) Carboxyl terminal deletion analysis of tryptophan hydroxylase. Biochim. Biophys. Acta 1342, 132–140.
Mockus S. M., Kumer S. C., and Vrana K. E. (1997b) A chimeric tyrosine/tryptophan hydroxylase: The tyrosine hydroxylase regulatory domain serves to stabilize enzyme activity. J. Mol. Neurosci. 9, 35–48.
Moran G. R., Daubner S. C., and Fitzpatrick P. L. (1998) Expression and characterization of the catalytic core of tryptophan hydroxylase. J. Biol. Chem. 273, 12,259–12,266.
Ota A., Yoshida S., and Nagatsu T. (1995) Deletion mutagenesis of human tyrosine hydroxylase type 1 regulatory domain. Biochem. Biophys. Res. Commun. 213, 1099–1106.
Pember S. O., Villafranca J. J., and Benkovic, S. J. (1987) Chromobacterium violaceum phenylalanine 4-monooxygenase. Methods Enzymol. 142, 50–56.
Quinsey N. S., Lenaghan C. M., and Dickson P. W. (1996) Identification of Gln313 and Pro327 as residues critical for substrate inhibition in tyrosine hydroxylase. J. Neurochem. 66, 908–914.
Ribeiro P., Wang Y., Citron B. A., and Kaufman S. (1993) Deletion mutagenesis of rat PC12 tyrosine hydroxylase regulatory and catalytic domains. J. Mol. Neurosci. 4, 125–139.
Vrana K. E., Rucker P., and Kumer S. C. (1994a) Recombinant rabbit tryptophan hydroxylase is a substrate cAMP-dependent protein kinase. Life Sci. 55, 1045–1052.
Vrana K. E., Walker S. J., Rucker P., and Liu X. (1994b) A carboxyl terminal leucine zipper is required for tyrosine hydroxylase tetramer formation. J. Neurochem. 63, 2014–2020.
Vrana S. L., Dworkin S. I., and Vrana K. E. (1993) Radioenzymatic assay for tryptophan hydroxylase: [3H2O] release assessed by charcoal adsorption. J. Neurosci. Methods 48, 123–129.
Walker J., Crowley P., Moreman A. D., and Barrett J. (1993) Biochemical properties of cloned glutathione S-transferases from Schistosoma mansoni and Schistosoma japonicum. Mol. Biochem. Parasitol. 61, 255–264.
Walker S. J., Liu X., Roskoski R. Jr., and Vrana K. E. (1994) Catalytic core of rat tyrosine hydroxylase: Terminal deletion analysis of bacterially-expressed enzyme. Biochim. Biophys. Acta 1206, 113–119.
Yang X. J. and Kaufman S. (1994) High-level expression and deletion mutagenesis of human tryptophan hydroxylase. Proc. Natl. Acad. Sci. USA 91, 6659–6663.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Yohrling, G.J., Mockus, S.M. & Vrana, K.E. Identification of amino-terminal sequences contributing to tryptophan hydroxylase tetramer formation. J Mol Neurosci 12, 23–34 (1999). https://doi.org/10.1385/JMN:12:1:23
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1385/JMN:12:1:23