Influence of the N terminus and the actin-binding motif of thymosin beta4 on its interaction with G-actin.
Thymosin beta(4) binds G-actin in a 1:1 ratio and prevents its aggregation to F-actin by sequestration. Substitution or modification of single amino acid residues within the N-terminal sequence 1 to 22 of thymosin beta(4) alters its interaction with G-actin. We generated thymosin beta(4) variants with amino acid substitutions within the N-terminal alpha-helix and the putative actin-binding motif. None of the E. coli-generated thymosin beta(4) variants was modified or acetylated at its N terminus. The stability of the complex of G-actin with nonacetylated thymosin beta(4) or beta(4)(A7V) is higher than the one with naturally occurring thymosin beta(4), which is always acetylated. The complex of G-actin with nonacetylated thymosin beta(4)(A7V,K18,19A) and beta(4)(K14,16,18,19A) is 15 times less stable compared to the complex with thymosin beta(4). The G-actin sequestering activities of all thymosin beta(4) variants correspond to their complex stabilities with G-actin, except for nonacetylated thymosin beta(4)(A7V), where it is attenuated. Thymosin beta(4)(Delta17-23) missing the putative actin-binding motif shows no interaction with G-actin.
Zoubek
Robert E
RE
Institute of Biochemistry, University Erlangen-Nuremberg, Fahrstr. 17, 91054 Erlangen, Germany. thymosin@biochem.uni-erlangen.de
Hannappel
Ewald
E
D000199:Actins / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013947:Thymosin / Q000737:chemistry* / Q000378:metabolism; D000099201:Thymosin beta(4)
D000199:Actins; D011994:Recombinant Proteins; D013947:Thymosin; D000099201:Thymosin beta(4)