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Phase transitions as intermediate steps in the formation of molecularly engineered protein fibers.

ABSTRACT: A central concept in molecular bioscience is how structure formation at different length scales is achieved. Here we use spider silk protein as a model to design new recombinant proteins that assemble into fibers. We made proteins with a three-block architecture with folded globular domains at each terminus of a truncated repetitive silk sequence. Aqueous solutions of these engineered proteins undergo liquid-liquid phase separation as an essential pre-assembly step before fibers can form by drawing in air. We show that two different forms of phase separation occur depending on solution conditions, but only one form leads to fiber assembly. Structural variants with one-block or two-block architectures do not lead to fibers. Fibers show strong adhesion to surfaces and self-fusing properties when placed into contact with each other. Our results show a link between protein architecture and phase separation behavior suggesting a general approach for understanding protein assembly from dilute solutions into functional structures.

SUBMITTER: Mohammadi P

PROVIDER: S-EPMC6123624 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Phase transitions as intermediate steps in the formation of molecularly engineered protein fibers.

Mohammadi Pezhman P Aranko A Sesilja AS Lemetti Laura L Cenev Zoran Z Zhou Quan Q Virtanen Salla S Landowski Christopher P CP Penttilä Merja M Fischer Wolfgang J WJ Wagermaier Wolfgang W Linder Markus B MB

Communications biology 20180702

A central concept in molecular bioscience is how structure formation at different length scales is achieved. Here we use spider silk protein as a model to design new recombinant proteins that assemble into fibers. We made proteins with a three-block architecture with folded globular domains at each terminus of a truncated repetitive silk sequence. Aqueous solutions of these engineered proteins undergo liquid-liquid phase separation as an essential pre-assembly step before fibers can form by draw ...[more]

PMID: 30271967

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Project description:BACKGROUND: Many studies have examined rules governing two aspects of protein structures: short segments and proteins' structural domains. Nevertheless, the organization and nature of the conformational space of segments with intermediate length between short segments and domains remain unclear. Conformational spaces of intermediate length segments probably differ from those of short segments. We investigated the identification and characterization of the boundary(s) between peptide-like (short segment) and protein-like (long segment) distributions. We generated ensembles embedded in globular proteins comprising segments 10-50 residues long. We explored the relationships between the conformational distribution of segments and their lengths, and also protein structural classes using principal component analysis based on the intra-segment Calpha-Calpha atomic distances. RESULTS: Our statistical analyses of segment conformations and length revealed critical dual transitions in their conformational distribution with segments derived from all four structural classes. Dual transitions were identified with the intermediate phase between the short segments and domains. Consequently, protein segment universes were categorized. i) Short segments (10-22 residues) showed a distribution with a high frequency of secondary structure clusters. ii) Medium segments (23-26 residues) showed a distribution corresponding to an intermediate state of transitions. iii) Long segments (27-50 residues) showed a distribution converging on one huge cluster containing compact conformations with a smaller radius of gyration. This distribution reflects the protein structures' organization and protein domains' origin. Three major conformational components (radius of gyration, structural symmetry with respect to the N-terminal and C-terminal halves, and single-turn/two-turn structure) well define most of the segment universes. Furthermore, we identified several conformational components that were unique to each structural class. Those characteristics suggest that protein segment conformation is described by compositions of the three common structural variables with large contributions and specific structural variables with small contributions. CONCLUSION: The present results of the analyses of four protein structural classes show the universal role of three major components as segment conformational descriptors. The obtained perspectives of distribution changes related to the segment lengths using the three key components suggest both the adequacy and the possibility of further progress on the prediction strategies used in the recent de novo structure-prediction methods.

Dataset Information

Phase transitions as intermediate steps in the formation of molecularly engineered protein fibers.

Publications

Phase transitions as intermediate steps in the formation of molecularly engineered protein fibers.

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