Environmental conditions impinge on dragline silk protein composition

Spider silk is a self-assembling biopolymer that outperforms most known materials in terms of its mechanical performance, despite its underlying weak chemical bonding based on H-bonds. While experimental studies have shown that the molecular structure of silk proteins has a direct influence on the stiffness, toughness and failure strength of silk, no molecular-level analysis of the nanostructure and associated mechanical properties of silk assemblies have been reported. Here, we report atomic-level structures of MaSp1 and MaSp2 proteins from the Nephila clavipes spider dragline silk sequence, obtained using replica exchange molecular dynamics, and subject these structures to mechanical loading for a detailed nanomechanical analysis. The structural analysis reveals that poly-alanine regions in silk predominantly form distinct and orderly beta-sheet crystal domains, while disorderly regions are formed by glycine-rich repeats that consist of 3 1 -helix type structures and beta-turns. Our structural predictions are validated against experimental data based on dihedral angle pair calculations presented in Ramachandran plots, alpha-carbon atomic distances, as well as secondary structure content. Mechanical shearing simulations on selected structures illustrate that the nanoscale behaviour of silk protein assemblies is controlled by the distinctly different secondary structure content and hydrogen bonding in the crystalline and semi-amorphous regions. Both structural and mechanical characterization results show excellent agreement with available experimental evidence. Our findings set the stage for extensive atomistic investigations of silk, which may contribute towards an improved understanding of the source of the strength and toughness of this biological superfibre.

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Cloning and Expression of Spider Dragline Silk Protein Gene in Escherichia coli and Eukaryotic Cells

Molecular Entomology ◽

10.5376/me.2011.02.0001 ◽

2011 ◽

Author(s):

Li Wenli

Keyword(s):

Escherichia Coli ◽

Protein Gene ◽

Silk Protein ◽

Cloning And Expression ◽

Eukaryotic Cells ◽

Dragline Silk ◽

Spider Dragline Silk

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Construct Synthetic Gene Encoding Artificial Spider Dragline Silk Protein and its Expression in Milk of Transgenic Mice

Animal Biotechnology ◽

10.1080/10495390601091024 ◽

2007 ◽

Vol 18 (1) ◽

pp. 1-12 ◽

Cited By ~ 47

Author(s):

Hong-Tao Xu ◽

Bao-Liang Fan ◽

Shu-Yang Yu ◽

Yin-Hua Huang ◽

Zhi-Hui Zhao ◽

...

Keyword(s):

Transgenic Mice ◽

Silk Protein ◽

Synthetic Gene ◽

Gene Encoding ◽

Dragline Silk ◽

Spider Dragline Silk

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Post-transcriptional control of mitochondrial protein composition in changing environmental conditions

Biochemical Society Transactions ◽

10.1042/bst20200250 ◽

2020 ◽

Vol 48 (6) ◽

pp. 2565-2578

Author(s):

Tatsuhisa Tsuboi ◽

Jordan Leff ◽

Brian M. Zid

Keyword(s):

Environmental Conditions ◽

Transcriptional Control ◽

Protein Import ◽

Mitochondrial Protein ◽

Protein Composition ◽

Mrna Translation ◽

Mitochondrial Structure ◽

Age Related ◽

And Function ◽

Post Transcriptional Regulation

In fluctuating environmental conditions, organisms must modulate their bioenergetic production in order to maintain cellular homeostasis for optimal fitness. Mitochondria are hubs for metabolite and energy generation. Mitochondria are also highly dynamic in their function: modulating their composition, size, density, and the network-like architecture in relation to the metabolic demands of the cell. Here, we review the recent research on the post-transcriptional regulation of mitochondrial composition focusing on mRNA localization, mRNA translation, protein import, and the role that dynamic mitochondrial structure may have on these gene expression processes. As mitochondrial structure and function has been shown to be very important for age-related processes, including cancer, metabolic disorders, and neurodegeneration, understanding how mitochondrial composition can be affected in fluctuating conditions can lead to new therapeutic directions to pursue.

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Protein Composition Correlates with the Mechanical Properties of Spider (Argiope trifasciata) Dragline Silk

Biomacromolecules ◽

10.1021/bm401110b ◽

2013 ◽

Vol 15 (1) ◽

pp. 20-29 ◽

Cited By ~ 20

Author(s):

Mohammad Marhabaie ◽

Thomas C. Leeper ◽

Todd A. Blackledge

Keyword(s):

Mechanical Properties ◽

Protein Composition ◽

Dragline Silk ◽

Argiope Trifasciata

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Molecular architecture and engineering of spider dragline silk protein

Progress in Natural Science Materials International ◽

10.1080/10020070512331342900 ◽

2005 ◽

Vol 15 (9) ◽

pp. 769-776 ◽

Cited By ~ 2

Author(s):

Zhang Hengmu ◽

Liu Jinyuan

Keyword(s):

Silk Protein ◽

Molecular Architecture ◽

Dragline Silk ◽

Spider Dragline Silk

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Environmentally Regulated Glycosome Protein Composition in the African Trypanosome

Eukaryotic Cell ◽

10.1128/ec.00086-13 ◽

2013 ◽

Vol 12 (8) ◽

pp. 1072-1079 ◽

Cited By ~ 18

Author(s):

Sarah Bauer ◽

James C. Morris ◽

Meredith T. Morris

Keyword(s):

Environmental Conditions ◽

Fluorescent Protein ◽

Protein Composition ◽

Bimodal Distribution ◽

Live Cells ◽

Reporter System ◽

Content Type ◽

Parasite Survival ◽

Low Glucose ◽

Parasite Populations

ABSTRACT Trypanosomes compartmentalize many metabolic enzymes in glycosomes, peroxisome-related microbodies that are essential to parasite survival. While it is understood that these dynamic organelles undergo profound changes in protein composition throughout life cycle differentiation, the adaptations that occur in response to changes in environmental conditions are less appreciated. We have adopted a fluorescent-organelle reporter system in procyclic Trypanosoma brucei by expressing a fluorescent protein (FP) fused to a glycosomal targeting sequence (peroxisome-targeting sequence 2 [PTS2]). In these cell lines, PTS2-FP is localized within import-competent glycosomes, and organelle composition can be analyzed by microscopy and flow cytometry. Using this reporter system, we have characterized parasite populations that differ in their glycosome composition. In glucose-rich medium, two parasite populations are observed; one population harbors glycosomes bearing the full repertoire of glycosome proteins, while the other parasite population contains glycosomes that lack the usual glycosome-resident proteins but do contain the glycosome membrane protein TbPEX11. Interestingly, these cells lack TbPEX13, a protein essential for the import of proteins into the glycosome. This bimodal distribution is lost in low-glucose medium. Furthermore, we have demonstrated that changes in environmental conditions trigger changes in glycosome protein composition. These findings demonstrate a level of procyclic glycosome diversity heretofore unappreciated and offer a system by which glycosome dynamics can be studied in live cells. This work adds to our growing understanding of how the regulation of glycosome composition relates to environmental sensing.

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