Tb4, or Thymosin beta 4, X-linked, is a human gene encoded by TMSB4X. It may also be known as: Thymosin beta-4; T beta-4; Fx; PTMB4; TB4X; TMSB4. The encoded protein has an amino acid length of 44 and a mass of 5.1 kDa. Tb4 is a member of the Thymosin beta family. Homologs of this gene exist in other organisms, including: Frog.