Influence of the N Terminus and the Actin-Binding Motif of Thymosin β4 on Its Interaction with G-Actin

• Published in: Annals of the New York Academy of Sciences Vol. 1112; no. 1; pp. 435 - 441
• Main Authors: ZOUBEK, ROBERT E., HANNAPPEL, EWALD
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01.09.2007
• Subjects: actin-binding motif; dissociation constant; G-actin; sequestration; thymosin β4; thymosin β4 variants
• ISSN: 0077-8923; 1749-6632
• DOI: 10.1196/annals.1415.026

:  Thymosin β4 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 β4 alters its interaction with G‐actin.We generated thymosin β4 variants with amino acid substitutions within the N‐terminal α‐helix and the putative actin‐binding motif. None of the E. coli‐generated thymosin β4 variants was modified or acetylated at its N terminus. The stability of the complex of G‐actin with nonacetylated thymosin β4 or β4A7V is higher than the one with naturally occurring thymosin β4, which is always acetylated. The complex of G‐actin with nonacetylated thymosin β4A7V,K18,19A and β4K14,16,18,19A is 15 times less stable compared to the complex with thymosin β4. The G‐actin sequestering activities of all thymosin β4 variants correspond to their complex stabilities with G‐actin, except for nonacetylated thymosin β4A7V, where it is attenuated. Thymosin β4Δ17–23 missing the putative actin‐binding motif shows no interaction with G‐actin.