Beta thymosins are a family of proteins which have in common a sequence of about 40 amino acids similar to the small protein thymosin (TB500). They are found almost exclusively in multicellular animals.
Thymosin was originally obtained from the thymus in company with several other small proteins which although named collectively "thymosins" are now known to be structurally and genetically unrelated and present in many different animal tissues. Thymosin beta-4 is a protein that is encoded by the TMSB4X gene and the protein consists of 44 amino acids. This gene encodes an actin sequestering protein which plays a role in regulation of actin polymerization. The protein is also involved in cell proliferation, migration, and differentiation. Work with cell cultures and experiments with animals have shown that administration of thymosin (TB500) can promote migration of cells, formation of blood vessels, maturation of stem cells, survival of various cell types and lowering of the production of pro-inflammatory cytokines. These multiple properties have provided the impetus for a world-wide series of on-going clinical trials of potential effectiveness of thymosin in promoting repair of wounds in skin, cornea and heart.
