THYROXINE-BINDING IN A TTR MET-119 KINDRED

• Type: Article in International Scientific Journal
• Date: 1993

Authors

ALVES, IL (Author) Other; DIVINO, CM (Author) Other; SCHUSSLER, GC (Author) Other; ALTLAND, K (Author) Other; ALMEIDA, MR (Author) ICBAS; PALHA, JA (Author) Other; COELHO, T (Author) Other; COSTA, PP (Author) Other; SARAIVA, MJM (Author) ICBAS

Journal

Title: Journal of Clinical Endocrinology and Metabolism

Vol. 77

Pages: 484-488

ISSN: 0021-972X

Publisher: Endocrine Society

Indexing

ISI Web of Knowledge - 32 Citations

Scopus - 35 Citations

Scientific classification

FOS: Medical and Health sciences > Clinical medicine

Other information

Authenticus ID: P-001-MTN

DOI: 10.1210/jc.77.2.484

Abstract (EN): Recently, a transthyretin variant, TTR Met 119, in which methionine substitutes for threonine 119, a component of the protein's iodothyronine binding site, was identified in individuals with transient euthyroid hyperthyroxinemia. Healthy carriers of Met 119 have normal serum thyroid hormone concentrations, but two studies of Met 119 carriers have differed as to whether T4 binding to TTR is increased An additional kindred has been identified by hybrid isoelectric focusing in an ongoing screening program for TTR variants in the Portuguese population with TTR Met 30 associated familial amyloidotic polyneuropathy. Cyanogen bromide peptide mapping and DNA restriction length polymorphism analyses showed that the propositus was a compound heterozygote for two TTR variants: Asn 90 and Met 119. Family analysis revealed that he inherited the TTR Met 119 variant from the mother and the TTR Asn 90 variant from the father. Neither the compound heterozygote nor his parents had symptoms of familial amyloidotic polyneuropathy. Serum dialysis with stepwise saturation of iodothyronine binding sites confirmed that TTR binding of T4 is increased in TTR Met 119. The increased binding is due to a higher TTR concentration rather than an increased association constant for T4. Because of the small proportion of serum T4 bound by TTR, increased T4 binding by TTR did not affect the ratio of free to bound T4 or T4 concentrations. In contrast, plasma retinol binding protein, almost all of which is bound by TTR, was elevated. The Asn 90 mutation does not affect either the concentration or the hormone binding characteristics of the protein. Possible long-term effects of these mutations and the combined heterozygotic state remain to be determined.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 5