Multiple fuzzy interactions in the moonlighting function of thymosin-β4

Abstract

Thymosine β4 (Tß4) is a 43 amino acid long intrinsically disordered protein (IDP), which was initially identified as an actin-binding and sequestering molecule. Later it was described to have multiple other functions, such as regulation of endothelial cell differentiation, blood vessel formation, wound repair, cardiac cell migration, and survival.1 The various functions of Tβ4 are mediated by interactions with distinct and structurally unrelated partners, such as PINCH, ILK, and stabilin-2, besides the originally identified G-actin. Although the cellular readout of these interactions and the formation of these complexes have been thoroughly described, no attempt was made to study these interactions in detail, and to elucidate the thermodynamic, kinetic, and structural underpinning of this range of moonlighting functions. Because Tβ4 is mostly disordered, and its 4 described partners are structurally unrelated (the CTD of stabilin-2 is actually fully disordered), it occurred to us that this system might be ideal to characterize the structural adaptability and ensuing moonlighting functions of IDPs. Unexpectedly, we found that Tβ4 engages in multiple weak, transient, and fuzzy interactions, i.e., it is capable of mediating distinct yet specific interactions without adapting stable folded structures.

Retracted: Molecular Motions and Interactions in Aqueous Solutions of Thymosin‐β4, Stabilin C‐Terminal Domain (CTD) and Their 1:1 Complex Studied by 1H NMR Spectroscopy

“…In a study addressing the complexes, Tβ 4 forms with its different protein partners, it was found that Tβ 4 engages in multiple fuzzy interactions, i.e., it is capable of mediating its distinct yet specific interactions without adapting distinct folded structures in the different complexes . Our previous wide‐line 1 H NMR measurements confirmed that there is more order in stabilin CTD than in Tβ4. The thermal trends of the mobile water fraction curves by NMR showed that isolated Tβ 4 and stabilin CTD, as well as their complex, are intrinsically disordered proteins.…”

“…The attributes introduced in works, moreover, the experimental results reported in Ref. and complemented here, are made use of in the thermodynamic characterization of the studied proteins. Besides their characterization, an important objective is to utilize thermodynamic properties in the description of the interaction between the proteins.…”

“…Besides their characterization, an important objective is to utilize thermodynamic properties in the description of the interaction between the proteins. An original experimental and interpretational method was applied and its efficiency was proven in this study of thymosin‐β 4 (Tβ 4 ), the cytoplasmic domain of stabilin‐2 (stabilin CTD), and their 1:1 complex …”

Water rotation barriers on protein molecular surfaces

“…We could provide evidence that the protein Df31 (Drosophila melanogaster histone chaperone involved in chromatin decondensation and stabilization) is intrinsically disordered along its entire length [20], the entire proline-rich region of CASK-interactive protein1 is intrinsically disordered [21], and that the results depend also on the protein structure (primary to quaternary level) [22] and its propensity to form a complex [23]. It was also found that a living organ, the eye lens, which contains various kinds of crystallins [24] in high concentrations, has characteristics similar to the protein solutions concerning the "non-freezing water phase" [25].…”

“…The details of the work on the mentioned protein families are to be published later. In our previous studies [16][17][18][19][20][21][22][23], we raised that a motional-narrowed wide-line NMR spectroscopic approach can be used for recording MD curves. The novelty of this study is to interpret the MD curves through energy potentials, which did not occur to us in the initial studies.…”