Actin-sequestering ability of thymosin beta 4, thymosin beta 4 fragments, and thymosin beta 4-like peptides as assessed by the DNase I inhibition assay.
Thymosin beta 4 containing 43 amino-acid residues belongs to a family of highly homologous peptides present at high concentrations in various species, cells, and tissues. Safer et al. [J. Biol. Chem. 266, 4029-4032 (1991)] have shown that thymosin beta 4 is an actin-sequestering peptide. Because DNase I is inhibited by G-actin and not by F-actin we employed this enzymatic assay to determine the actin sequestering properties of 4 other thymosin beta 4-like peptides and fragments of thymosin beta 4 generated by enzymatic digestions. Thymosin beta 4 sequesters G-actin at a 1 to 1 ratio an thereby inhibits its polymerisation to F-actin in high salt solution. The oxidation of the single methionine residue at position 6 does not abolish its actin-sequestering properties. However neither thymosin beta 4 24-43 nor thymosin beta 4 13-43 inhibit the polymerisation of G-actin. We conclude from this that some structural features in the amino-acid sequence of thymosin beta 4 before position 13 are obligatory for its biological function. Oxidized thymosin beta 4 (beta 4-sulfoxide) as well as four other thymosin beta 4-like peptides were shown to be actin-sequestering peptides like thymosin beta 4.
Hannappel
E
E
Institut für Biochemie, Medizinische Fakultät, Universität Erlangen-Nürnberg.
Wartenberg
F
F
D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D004247:DNA / Q000032:analysis; D003850:Deoxyribonuclease I / Q000037:antagonists & inhibitors*; D010450:Endopeptidases / Q000378:metabolism; D008715:Methionine / Q000032:analysis; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology; D013947:Thymosin / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology; D014357:Trypsin; D000099201:Thymosin beta(4)
D000199:Actins; D004247:DNA; D003850:Deoxyribonuclease I; D010450:Endopeptidases; D008715:Methionine; D010446:Peptide Fragments; D013947:Thymosin; D014357:Trypsin; D000099201:Thymosin beta(4)