Thymosin beta 10, a new analog of thymosin beta 4 in mammalian tissues.

A new analog of thymosin beta 4 has been isolated from tissues of several mammalian species. This peptide, designated thymosin beta 10, is composed of 42 amino acid residues and shows 75% sequence homology with thymosin beta 4. It occurs together with thymoxin beta 4 in a variety of tissues including spleen, liver, and thymus and also in several cultured cell lines. In the spleen of rat, mouse, cat, and man, the new peptide accounts for approximately 0.02% by weight of the total protein. In the calf it is replaced by another homologous peptide, designated thymosin beta 9, whose structure has been reported.