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Study · In vitro (cell-free) · 1999

3 results

Profilin promotes barbed-end actin filament assembly without lowering the critical concentration.

Kang F, Purich DL, Southwick FS

The Journal of biological chemistry1 Dec 1999Cited by 134 (Europe PMC)

PMID10601251 (opens in a new tab)DOI10.1074/jbc.274.52.36963 (opens in a new tab)PepBankPUB-10601251
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Summary

The mechanism of profilin-promoted actin polymerization has been systematically reinvestigated. Rates of barbed-end elongation onto Spectrin.4.1. Actin seeds were measured by right angle light scattering to avoid confounding effects of pyrenyl-actin, and KINSIM was used to analyze elongation progress curves. Without thymosin-beta4, both actin and Profilin. Actin (P.A) are competent in barbed-end polymerization, and kinetic simulations yielded the same bimolecular rate constant ( approximately 10 x 10(6) M(-1) s(-1)) for actin monomer or Profilin. Actin. When measured in the absence of profilin, actin assembly curves over a 0.7-4 microM thymosin-beta4 concentration range fit a simple monomer sequestering model (1 microM K(D) for Thymosin-beta4. Actin). The corresponding constant for thymosin-beta4.pyrenyl-Actin, however, was significantly higher ( approximately 9-10 microM), suggesting that the fluorophore markedly weakens binding to thymosin-beta4. With solutions of actin (2 microM) and thymosin-beta4 (2 or 4 microM), the barbed-end assembly rate rose with increasing profilin concentration (0.7-2 microM). Actin assembly in presence of thymosin-beta4 and profilin fit a simple thermodynamic energy cycle, thereby disproving an earlier claim (D. Pantaloni and M.-F. Carlier (1993) Cell 75, 1007-1014) that profilin promotes nonequilibrium filament assembly by accelerating hydrolysis of filament-bound ATP. Our findings indicate that profilin serves as a polymerization catalyst that captures actin monomers from Thymosin-beta4. Actin and ushers actin as a Profilin. Actin complex onto growing barbed filament ends.
CC BYText from Europe PMC. Highlighted sentences are the source of results.

Results from this study3

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

  1. 01LabIn vitro (cell-free)Activity measurement

    In a cell-free assay, actin assembly curves with 0.7-4 microM thymosin-beta4 fitted a simple monomer sequestering model with a KD of 1 microM for thymosin-beta4 binding to actin.

    In plain wordsIn lab tests, thymosin-beta4 bound actin monomers with a dissociation constant of about 1 microM.

    Peptide
    Thymosin beta-4 (human)
    Outcome
    Not applicableTβ4 binding to actin (KD)
    Study

    n: not reported in source

    actin polymerization assay
    Outcome group
    Receptor activity and mechanism · Pharmacology
    Studied dose
    0.7-4 microMAs given in this study.

    Measurements

    KD thymosin-beta4 and actin
    1 µM
    unlabeled actin

    Source sentences

    Summary
    When measured in the absence of profilin, actin assembly curves over a 0.7-4 microM thymosin-beta4 concentration range fit a simple monomer sequestering model (1 microM K(D) for Thymosin-beta4. Actin).
  2. 02LabIn vitro (cell-free)Activity measurement

    In a cell-free assay, the KD for thymosin-beta4 binding to pyrenyl-actin was significantly higher (approximately 9-10 microM), suggesting that the fluorophore weakens binding to thymosin-beta4.

    In plain wordsIn lab tests, thymosin-beta4 bound pyrenyl-labeled actin more weakly than plain actin.

    Peptide
    Thymosin beta-4 (human)
    Outcome
    Not applicableTβ4 binding to pyrenyl-actin (KD)
    Study

    n: not reported in source

    actin polymerization assay
    Outcome group
    Receptor activity and mechanism · Pharmacology
    Studied dose
    Dose not stated

    Measurements

    KD thymosin-beta4 and pyrenyl-actin
    9 to 10 µM
    pyrenyl-actin

    Source sentences

    Summary
    The corresponding constant for thymosin-beta4.pyrenyl-Actin, however, was significantly higher ( approximately 9-10 microM), suggesting that the fluorophore markedly weakens binding to thymosin-beta4.

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

    In a cell-free assay with actin and thymosin-beta4, the barbed-end assembly rate rose with increasing profilin concentration (0.7-2 microM).

    In plain wordsIn lab tests with actin and thymosin-beta4 present, adding more profilin sped up filament assembly.

    Peptide
    Thymosin beta-4 (human)
    Outcome
    IncreaseBarbed-end assembly rate with thymosin-beta4 and profilin
    Study

    n: not reported in source

    actin polymerization assay
    Outcome group
    Receptor activity and mechanism · Pharmacology

    Source sentences

    Summary
    With solutions of actin (2 microM) and thymosin-beta4 (2 or 4 microM), the barbed-end assembly rate rose with increasing profilin concentration (0.7-2 microM).

    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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