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Crowding alters F-actin secondary structure and hydration.

ABSTRACT: Actin, an important component of eukaryotic cell cytoskeleton, regulates cell shape and transport. The morphology and biochemical properties of actin filaments are determined by their structure and protein-protein contacts. Crowded environments can organize filaments into bundles, but less is known about how they affect F-actin structure. This study used 2D IR spectroscopy and spectral calculations to examine how crowding and bundling impact the secondary structure and local environments in filaments and weakly or strongly bundled networks. The results reveal that bundling induces changes in actin's secondary structure, leading to a decrease in β-sheet and an increase in loop conformations. Strongly bundled networks exhibit a decrease in backbone solvent exposure, with less perturbed α-helices and nearly "locked" β-sheets. Similarly, the loops become less hydrated but maintain a dynamic environment. These findings highlight the role of loop structure in actin network morphology and stability under morphology control by PEG.

SUBMITTER: Chen X

PROVIDER: S-EPMC10475093 | biostudies-literature | 2023 Sep

REPOSITORIES: biostudies-literature

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Crowding alters F-actin secondary structure and hydration.

Chen Xiaobing X Roeters Steven J SJ Cavanna Francis F Alvarado José J Baiz Carlos R CR

Communications biology 20230902 1

Actin, an important component of eukaryotic cell cytoskeleton, regulates cell shape and transport. The morphology and biochemical properties of actin filaments are determined by their structure and protein-protein contacts. Crowded environments can organize filaments into bundles, but less is known about how they affect F-actin structure. This study used 2D IR spectroscopy and spectral calculations to examine how crowding and bundling impact the secondary structure and local environments in fila ...[more]

PMID: 37660224

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Project description:We demonstrate that the effect of protein crowding is critically dependent on the stability of the protein's hydration shell, which can dramatically vary between different proteins. In the human eye lens, γS-crystallin (γS-WT) forms a densely packed transparent hydrogel with a high refractive index, making it an ideal system for studying the effects of protein crowding. A single point mutation generates the cataract-related variant γS-G18V, dramatically altering the optical properties of the eye lens. This system offers an opportunity to explore fundamental questions regarding the effect of protein crowding, using γS-WT and γS-G18V: (i) how do the diffusion dynamics of hydration water change as a function of protein crowding?; and (ii) upon hydrogel formation of γS-WT, has a dynamic transition occurred generating a single population of hydration water, or do populations of bulk and hydration water coexist? Using localized spin probes, we separately probe the local translational diffusivity of both surface hydration and interstitial water of γS-WT and γS-G18V in solution. Surprisingly, we find that under the influence of hydrogel formation at highly crowded γS-WT concentrations up to 500 mg/mL, the protein hydration shell remains remarkably dynamic, slowing by less than a factor of 2, if at all, compared to that in dilute protein solutions of ∼5 mg/mL. Upon self-crowding, the population of this robust surface hydration water increases, while a significant bulk-like water population coexists even at ∼500 mg/mL protein concentrations. In contrast, surface water of γS-G18V irreversibly dehydrates with moderate concentration increases or subtle alterations to the solution conditions, demonstrating that the effect of protein crowding is highly dependent on the stability of the protein-specific hydration shell. The core function of γS-crystallin in the eye lens may be precisely its capacity to preserve a robust hydration shell, whose stability is abolished by a single G18V mutation.

Dataset Information

Crowding alters F-actin secondary structure and hydration.

Publications

Crowding alters F-actin secondary structure and hydration.

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