ISSN:
1423-0127
Keywords:
Catalytic activity
;
Leucine zipper
;
Tetramer formation
;
Tyrosine hydroxylase
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract The native form of tyrosine hydroxylase (TH) is a homotetramer which consists of four identical subunits each with an MW of approximately 60 kD. The relationships between the catalytic activity of TH and oligomerization of the enzyme have not yet been characterized. We have investigated, by deletion and/or substitution mutagenesis, the involvement of the leucine zipper (LZ) motifs in the oligomer formation of TH and its relation to catalytic activity. Our results demonstrate that deletion of the carboxyl-terminal LZ (LZ-C) abolishes tetramer formation. Interruption of the other two LZ motifs (LZ-A and LZ-B), located in a central region of the catalytic domain by substitution of Leu to Pro at residues 294 and 301 or 386 and 393 has no effect on the tetramer formation of TH. However, the interruption of LZ-A and LZ-B abolishes TH enzymatic activity. The substitution of Leu residues 188 and 190 with Pro at the regulatory domain of TH reduces enzymatic TH activity without affecting tetramer formation. Thus, LZ-C is required for tetramer formation, while LZ-A and LZ-B seem to be involved in the catalytic activity without affecting the tetramer formation of TH.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02257963
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