The relationship between the structure of the N-terminal sequence of trans-thyretin (TTR) and the binding of thyroid hormone was studied. A recom-binant human TTR and two derivatives of Crocodylus porosusTTRs, one with the N-terminal sequence replaced by that of human TTR (human⁄crocTTR), the other with the N-terminal segment removed (trun-cated crocTTR), were synthesized inPichia pastoris.