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Study · In vitro (cell-free) · 2001

4 results

Formation and implications of a ternary complex of profilin, thymosin beta 4, and actin.

Yarmola EG, Parikh S, Bubb MR

The Journal of biological chemistry28 Sept 2001Cited by 38 (Europe PMC)

PMID11579089 (opens in a new tab)DOI10.1074/jbc.m105723200 (opens in a new tab)PepBankPUB-11579089
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Summary

Data from affinity chromatography, analytical ultracentrifugation, covalent cross-linking, and fluorescence anisotropy show that profilin, thymosin beta(4), and actin form a ternary complex. In contrast, steady-state assays measuring F-actin concentration are insensitive to the formation of such a complex. Experiments using a peptide that corresponds to the N terminus of thymosin beta(4) (residues 6-22) confirm the presence of an extensive binding surface between actin and thymosin beta(4), and explain why thymosin beta(4) and profilin can bind simultaneously to actin. Surprisingly, despite much lower affinity, the N-terminal thymosin beta(4) peptide has a very slow dissociation rate constant relative to the intact protein, consistent with a catalytic effect of the C terminus on conformational change occurring at the N terminus of thymosin beta(4). Intracellular concentrations of thymosin beta(4) and profilin may greatly exceed the equilibrium dissociation constant of the ternary complex, inconsistent with models showing sequential formation of complexes of profilin-actin or thymosin beta(4)-actin during dynamic remodeling of the actin cytoskeleton. The formation of a ternary complex results in a very large amplification mechanism by which profilin and thymosin beta(4) can sequester much more actin than is possible for either protein acting alone, providing an explanation for significant sequestration even if molecular crowding results in a very low critical concentration of actin in vivo.
CC BYText from Europe PMC. Highlighted sentences are the source of results.

Results from this study4

1 result from studies that gave the peptide. No result from this study comes from people.

  1. 01LabIn vitro (cell-free)Mechanism

    In vitro, profilin, thymosin beta(4) and actin form a ternary complex.

    In plain wordsIn lab tests, Tbeta4, profilin and actin bind together in one complex.

    Peptide
    Thymosin beta-4 (human)
    Outcome
    Not applicableTernary complex of profilin, Tbeta4 and actin
    Study

    n: not reported in source

    Purified proteins in vitro
    Outcome group
    Receptor activity and mechanism · Whole body
    Studied dose
    Dose not stated

    Source sentences

    Summary
    Data from affinity chromatography, analytical ultracentrifugation, covalent cross-linking, and fluorescence anisotropy show that profilin, thymosin beta(4), and actin form a ternary complex.

Studies that did not test the peptide alone3

In this study, Thymosin beta-4 (human) was a lab tool or a carrier, part of a mix, or the subject of a lab method. These results are not evidence about taking Thymosin beta-4 (human).

  1. 02LabNot a test of Thymosin beta-4 (human) aloneIn vitro (cell-free)Mechanism

    In vitro, a peptide of Tbeta4 residues 6-22 confirmed an extensive binding surface between actin and Tbeta4, and explained simultaneous binding of Tbeta4 and profilin to actin.

    In plain wordsIn lab tests, a piece of Tbeta4 showed that Tbeta4 binds actin over a large surface and can bind together with profilin.

    Peptide
    Thymosin beta-4 (human)
    Outcome
    Not applicableBinding surface of Tbeta4 N-terminal peptide (residues 6-22) with actin
    Study

    n: not reported in source

    Purified proteins in vitro
    Outcome group
    Receptor activity and mechanism · Whole body

    Source sentences

    Summary
    Experiments using a peptide that corresponds to the N terminus of thymosin beta(4) (residues 6-22) confirm the presence of an extensive binding surface between actin and thymosin beta(4), and explain why thymosin beta(4) and profilin can bind simultaneously to actin.

    In this study, Thymosin beta-4 (human) was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Thymosin beta-4 (human).

  2. 03LabNot a test of Thymosin beta-4 (human) aloneIn vitro (cell-free)Mechanism

    In vitro, the N-terminal Tbeta4 peptide had much lower affinity but a very slow dissociation rate constant relative to the intact protein.

    In plain wordsIn lab tests, a piece of Tbeta4 bound actin more weakly than the whole protein but let go of it very slowly.

    Peptide
    Thymosin beta-4 (human)
    Outcome
    Not applicableDissociation rate of Tbeta4 N-terminal peptide
    Study

    n: not reported in source

    Purified proteins in vitro
    Outcome group
    Receptor activity and mechanism · Whole body

    Source sentences

    Summary
    Surprisingly, despite much lower affinity, the N-terminal thymosin beta(4) peptide has a very slow dissociation rate constant relative to the intact protein, consistent with a catalytic effect of the C terminus on conformational change occurring at the N terminus of thymosin beta(4).

    In this study, Thymosin beta-4 (human) was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Thymosin beta-4 (human).

  3. 04LabNot a test of Thymosin beta-4 (human) aloneIn vitro (cell-free)Mechanism

    In vitro, formation of the ternary complex lets profilin and Tbeta4 together sequester much more actin than either protein acting alone.

    In plain wordsIn lab tests, profilin and Tbeta4 together held back much more actin than either protein alone.

    Peptide
    Thymosin beta-4 (human)
    Outcome
    Not applicableActin sequestration by profilin and Tbeta4 together
    Study

    n: not reported in source

    Purified proteins in vitro
    Outcome group
    Receptor activity and mechanism · Whole body

    Source sentences

    Summary
    The formation of a ternary complex results in a very large amplification mechanism by which profilin and thymosin beta(4) can sequester much more actin than is possible for either protein acting alone, providing an explanation for significant sequestration even if molecular crowding results in a very low critical concentration of actin in vivo.

    In this study, Thymosin beta-4 (human) was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Thymosin beta-4 (human).

AI wrote and checked these results. AI can make mistakes, so check important results against the source.

Version history

PepBank keeps every version of the data on this study. Status changes from Retraction Watch, Europe PMC and Crossref are listed with their source.

  1. Version 2Current

    13 Oct 2026, 01:52 UTC

    Study results updated

  2. Version 1

    12 Oct 2026, 18:17 UTC

    First added · source update from Europe PMC

Subjects

Terms as the source lists them.

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