Repolymerization of actin from actin:thymosin beta4 complex induced by diaphanous related formins and gelsolin.
The beta-thymosins are peptides of about 5 kDa molecular mass. Thymosin beta4 (Tbeta4) is the most ubiquitous member of this family and composed of 43 residues. Initially the beta-thymosins were supposed to be specifically produced and released by the thymic gland and to possess hormonal activities modulating the immune response. However, it was later noticed that beta-thymosins are present in the cytoplasm of almost all eukaryotic cells. Especially high concentrations of Tbeta4 were detected in hematopoetic cells, like polymorpho-nuclear leucocytes and in platelets. In these cells the main intracellular function of the beta-thymosins is to bind to monomeric actin and to inhibit its polymerization to filamentous actin. Thus Tbeta4 allows resting eukaryotic cells to maintain a high concentration of monomeric actin, although the intracellular ionic conditions would favor its almost complete polymerization to F-actin. Thereby monomeric actin is sequestered from the dynamic assembly and disassembly processes of the actin cytoskeleton that constantly occur intracellularly.
Department of Anatomy & Embryology, Ruhr-University Bochum, D-44780 Bochum, Germany. hans.g.mannherz@rub.de
Hans Georg
HG
Mannherz
Antonina Joanna
AJ
Mazur
Brigitte
B
Jockusch
D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D018260:Gelsolin / Q000378:metabolism*; D006801:Humans; D008709:Methenamine / Q000378:metabolism; D008970:Molecular Weight; D011485:Protein Binding; D013947:Thymosin / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D000099201:Thymosin beta(4)
D000199:Actins; D018260:Gelsolin; D008709:Methenamine; D013947:Thymosin; D000099201:Thymosin beta(4)