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Petersen CE, Ha CE, Harohalli K, Park DS, Feix JB, Isozaki O, Bhagavan NV. Structural Investigations of a New Familial Dysalbuminemic Hyperthyroxinemia Genotype. Clin Chem 1999. [DOI: 10.1093/clinchem/45.8.1248] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
AbstractBackground: In a previous study, we found that the amino acid substitution R218H in human serum albumin (HSA) was the cause of familial dysalbuminemic hyperthyroxinemia (FDH) in several Caucasian patients. Subsequently the substitution R218P was shown to be the cause of FDH in several members of a Japanese family. This study attempts to resolve discrepancies in the only other study of R218P HSA and identifies two new Japanese R218P FDH patients unrelated to those described previously.Methods and Results: Recombinant R218H, R218P, and wild-type HSA were synthesized in yeast, and the affinities of these HSA species for l- and d-thyroxine were determined using fluorescence spectroscopy. The dissociation constants for the binding of wild-type, R218P, and R218H HSA to l-thyroxine were 1.44 × 10−6, 2.64 × 10−7, and 2.49 × 10−7 mol/L, respectively. The circular dichroism spectra of thyroxine bound to R218H and R218P HSA were markedly different, indicating that the structure of the thyroxine/HSA complex is different for either protein.Conclusions: The Kd values for l-thyroxine bound to R218P and R218H HSA determined in this study were similar. The extremely high serum total-thyroxine concentrations reported previously for R218P FDH patients (10-fold higher than those reported for R218H FDH patients) are not consistent with the Kd values determined in this study. Possible explanations for these discrepancies are discussed.
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Affiliation(s)
- Charles E Petersen
- Department of Biochemistry and Biophysics, University of Hawaii, 1960 East-West Rd., Honolulu, HI 96822
| | - Chung-Eun Ha
- Department of Biochemistry and Biophysics, University of Hawaii, 1960 East-West Rd., Honolulu, HI 96822
| | - Krishna Harohalli
- Department of Biochemistry and Biophysics, University of Hawaii, 1960 East-West Rd., Honolulu, HI 96822
| | - David S Park
- Department of Biochemistry and Biophysics, University of Hawaii, 1960 East-West Rd., Honolulu, HI 96822
| | - Jimmy B Feix
- Biophysics Research Institute, Medical College of Wisconsin, 8701 Watertown Plank Rd., P.O. Box 26509, Milwaukee, WI 53226
| | - Osamu Isozaki
- Department of Medicine, Institute of Clinical Endocrinology, Tokyo Women’s Medical College, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162, Japan
| | - Nadhipuram V Bhagavan
- Department of Biochemistry and Biophysics, University of Hawaii, 1960 East-West Rd., Honolulu, HI 96822
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Petersen CE, Ha CE, Jameson DM, Bhagavan NV. Mutations in a specific human serum albumin thyroxine binding site define the structural basis of familial dysalbuminemic hyperthyroxinemia. J Biol Chem 1996; 271:19110-7. [PMID: 8702585 DOI: 10.1074/jbc.271.32.19110] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The familial dysalbuminemic hyperthyroxinemia (FDH) phenotype results from a natural human serum albumin (HSA) mutant with histidine instead of arginine at amino acid position 218. This mutation results in an enhanced affinity for thyroxine. Site-directed mutagenesis and a yeast protein expression system were used to synthesize wild type HSA and FDH HSA as well as several other HSA mutants. Studies on the binding of thyroxine to these HSA species using equilibrium dialysis and quenching of tryptophan 214 fluorescence suggest that the FDH mutation affects a single thyroxine binding site located in the 2A subdomain of HSA. Site-directed mutagenesis of HSA and thyroxine analogs were used to obtain information about the mechanism of thyroxine binding to both wild type and FDH HSA. These studies suggest that the guanidino group of arginine at amino acid position 218 in wild type HSA is involved in an unfavorable binding interaction with the amino group of thyroxine, whereas histidine at amino acid position 218 in FDH HSA is involved in a favorable binding interaction with thyroxine. Neither arginine at amino acid position 222 nor tryptophan at amino acid position 214 appears to favorably influence the binding of thyroxine to wild type HSA.
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Affiliation(s)
- C E Petersen
- Department of Biochemistry and Biophysics, University of Hawaii, Honolulu, Hawaii 96822, USA
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Okabe N, Okamura M, Tokuoka R, Tomita KI. The Interaction between α-Helical Poly-L-lysine and Thyroxine as Measured by Circular Dichroism. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 1981. [DOI: 10.1246/bcsj.54.3790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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