Two precursors of thyrotropin-releasing hormone from skin of Xenopus laevis. Each contains seven copies of the end product.

From the skin of Xenopus laevis, the cloned cDNAs of two precursors of thyrotropin-releasing hormone have been isolated and sequenced. These encode almost identical precursor polypeptides each containing seven copies of the end product flanked by typical prohormones processing signals. Northern blot analysis has corroborated the existence of two thyrotropin-releasing hormone precursor mRNAs of similar size as the cloned cDNA and demonstrated the existence of a third smaller species as well. Two or more mRNAs for this precursor are also present in the brain and eyes of X. laevis adults and tadpoles.