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Study · In vitro (cell-free) · 2004

2 results

Effects of profilin and thymosin beta4 on the critical concentration of actin demonstrated in vitro and in cell extracts with a novel direct assay.

Yarmola EG, Bubb MR

The Journal of biological chemistry7 Jun 2004Cited by 23 (Europe PMC)

PMID15184365 (opens in a new tab)DOI10.1074/jbc.m404392200 (opens in a new tab)PepBankPUB-15184365
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Summary

The free actin concentration at steady state, Ac, is a variable that determines how actin regulatory proteins influence the extent of actin polymerization. We describe a novel method employing fluorescence anisotropy to directly measure Ac in any sample after the addition of a trace amount of labeled thymosin beta4 or thymosin beta4 peptide. Using this assay, we confirm earlier theoretical work on the helical polymerization of actin and confirm the effects of actin filament-stabilizing drugs and capping proteins on Ac, thereby validating the assay. We also confirm a controversial prior observation that profilin lowers the critical concentration of Mg2+-actin. A general mechanism is proposed to explain this effect, and the first quantitative dose-response curve for the effect of profilin on Ac facilitates its evaluation. This mechanism also predicts the effect of profilin on critical concentration in the presence of the limited amount of capping protein, which is the condition often found in cells, and the effect of profilin on critical concentration in cell extracts is demonstrated for the first time. Additionally, nonlinear effects of thymosin beta4 on the steady state amount of F-actin are explained by the observed changes in Ac. This assay has potential in vivo applications that complement those demonstrated in vitro.
CC BYText from Europe PMC. Highlighted sentences are the source of results.

Results from this study2

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

  1. 01LabIn vitro (cell-free)Mechanism

    In lab tests, thymosin beta4 had nonlinear effects on the steady state amount of F-actin, explained by the observed changes in free actin concentration.

    In plain wordsIn lab tests, thymosin beta4 changed the amount of filamentous actin in a nonlinear way.

    Peptide
    Thymosin beta-4 (human)
    Outcome
    MixedEffect of thymosin beta4 on steady state F-actin amount
    Study

    n: not reported in source

    purified actin and cell extracts
    Outcome group
    Receptor activity and mechanism · Pharmacology
    Studied dose
    Dose not stated

    Source sentences

    Summary
    Additionally, nonlinear effects of thymosin beta4 on the steady state amount of F-actin are explained by the observed changes in Ac.

Studies that did not test the peptide alone1

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)Other

    A novel fluorescence anisotropy method using a trace amount of labeled thymosin beta4 measured the free actin concentration at steady state in any sample.

    In plain wordsIn lab tests, a new method that uses labeled thymosin beta4 measured the free actin level in a sample.

    Peptide
    Thymosin beta-4 (human)
    Outcome
    Not applicableAssay of free actin concentration using labeled thymosin beta4
    Study

    n: not reported in source

    fluorescence anisotropy assay
    Outcome group
    Receptor activity and mechanism · Pharmacology

    Source sentences

    Summary
    We describe a novel method employing fluorescence anisotropy to directly measure Ac in any sample after the addition of a trace amount of labeled thymosin beta4 or thymosin beta4 peptide.

    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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