Isolation, characterization, cDNA cloning and gene expression of an avian transthyretin

Implications for the evolution of structure and function of transthyretin in vertebrates


  • Note. The novel nucleotide sequence data published here have been deposited with the EMBL sequence data bank.

Correspondence to G. Schreiber, Russell Grimwade School of Biochemistry, University of Melbourne, Parkville, Victoria, Australia 3052


A chicken liver cDNA library was constructed in bacteriophage λgt10. A full-length transthyretin cDNA clone was identified by screening with rat transthyretin cDNA and was sequenced. A three-dimensional model of chicken transthyretin was obtained by computer-graphics-based prediction from the derived amino acid sequence for chicken transthyretin and from the structure of human transthyretin determined by X-ray diffraction analysis [Blake, C. C. F., Geisow, M. J., Oatley, S. J., Rérat, B. & Rérat, C. (1978) J. Mol. Biol. 121, 339–356]. The similarity of the amino acid sequences of chicken and human transthyretins was 75% overall and 100% for the central channel containing the thyroxine-binding site. Also, the organization of the transthyretin gene into exons and introns and the tissue specificity of expression of the transthyretin gene were similar in chicken and mammals, despite an evolutionary distance of about 3 × 108 years from their common ancestor, the Cotylosaurus. By far the highest levels of transthyretin mRNA were found in choroid plexus. The data suggest a fundamental role for the cerebral expression of transthyretin in all vertebrates. It has been proposed that this role is the transport of thyroxine from the bloodstream to the brain [Schreiber, G., Aldred, A. R., Jaworowski, A., Nilsson, C., Achen, M. G. & Segal, M. B. (1990) Am. J. Physiol. 258, R338–R345].


Restriction endonucleases (EC


DNA polymerase (EC


SP6 RNA polymerase (EC


DNase I (EC


pancreatic RNase (EC


ribonuclease T1 (EC


reverse transcriptase (EC