Plays an important role in the organization of the cytoskeleton (PubMed:10848969, PubMed:1999398). Binds to and sequesters actin monomers (G actin) and therefore inhibits actin polymerization (PubMed:10848969, PubMed:1999398). {ECO:0000269|PubMed:10848969, ECO:0000269|PubMed:1999398}. [Hemoregulatory peptide AcSDKP]: Potent inhibitor of bone marrow derived stem cell differentiation (PubMed:7694679). Acts by inhibits the entry of hematopoietic pluripotent stem cells into the S- phase (By similarity). {ECO:0000250|UniProtKB:P62326, ECO:0000269|PubMed:7694679}. This is the function of TMSB4X (thymosin beta 4 X-linked, ENSG00000205542).