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Tyrosine 130 is an important outer ring donor for thyroxine formation in thyroglobulin
A D Dunn1, C M Corsi, H E Myers
1Division of Endocrinology, Department of Medicine, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA. add7k@virginia.edu
The Journal of Biological Chemistry
|September 17, 1998
Summary
Researchers identified Tyr130 as a key donor site for thyroid hormone synthesis in thyroglobulin. This finding helps pinpoint the specific tyrosine residues involved in forming thyroid hormones.
Area of Science:
- Biochemistry
- Endocrinology
- Molecular Biology
Background:
- Thyroid hormone synthesis involves coupling iodotyrosine molecules within thyroglobulin.
- Previous studies identified hormone acceptor sites but not the primary iodotyrosine donor sites.
Purpose of the Study:
- To identify the principal iodotyrosine donor residues involved in thyroid hormone formation.
- To elucidate the specific donor site for the outer ring of iodothyronine.
Main Methods:
- Incorporation of [14C]tyrosine into beef thyroid slices and subsequent isolation of labeled thyroglobulin.
- Peptide fragmentation using trypsin and endoproteinase Glu-C, followed by mass spectrometry and Edman degradation.
- Identification of labeled pyruvate and specific peptide fragments.
Main Results:
- Tyrosine residue 130 (Tyr130) was identified as a donor site, modified to pyruvate.
- A specific peptide fragment (residues 130-146) containing pyruvate at position 130 was identified.
- 14C-labeled pyruvate was found in the same fraction as the modified peptide.
Conclusions:
- Tyr130 is a significant donor site for the outer iodothyronine ring.
- Tyr5 is proposed as the likely acceptor site due to proximity and prominent iodination.
- The N-terminal region of thyroglobulin is capable of forming T4 independently.