Complete amino acid sequence of bovine thymosin beta 4: a thymic hormone that induces terminal deoxynucleotidyl transferase activity in thymocyte populations

Proc Natl Acad Sci U S A. 1981 Feb;78(2):1162-6. doi: 10.1073/pnas.78.2.1162.


The amino acid sequence of thymosin beta 4, a polypeptide isolated from calf thymus, was determined. Thymosin beta 4 is composed of 43 amino acid residues and has a molecular weight of 4982 and an isoelectric point of 5.1. The NH2 terminus of the peptide is blocked by an acetyl group. This molecule induces expression of terminal deoxynucleotidyl transferase (DNA nucleotidylexotransferase, EC in transferase-negative murine thymocytes in vivo and in citro. Thus, it appears that thymosin beta 4 acts on lymphoid stem cells and may control the early stages of the maturation process of thymus-dependent lymphocytes. This peptide is one of several present in thymosin fraction 5 that participates in the regulation, differentiation, and function of thymus-dependent thymocytes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cattle
  • Cyanogen Bromide
  • DNA Nucleotidylexotransferase / biosynthesis*
  • DNA Nucleotidyltransferases / biosynthesis*
  • Enzyme Induction
  • Hydrocortisone / pharmacology
  • Mice
  • Mice, Inbred BALB C
  • Molecular Weight
  • Peptide Fragments / analysis
  • Thymosin* / pharmacology
  • Thymus Gland / drug effects
  • Thymus Gland / enzymology*
  • Thymus Hormones* / pharmacology


  • Peptide Fragments
  • Thymus Hormones
  • Thymosin
  • DNA Nucleotidyltransferases
  • DNA Nucleotidylexotransferase
  • Cyanogen Bromide
  • Hydrocortisone