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Team:Groningen/Silk/Protein
From 2013.igem.org
Silk protein
The spider silk protein is a fibrous protein. It does not have a folded state on its own; it is able to assemble (multimerize) with multiple identical proteins to form the silk. The protein consists of roughly 3 motifs, each featuring a particular secondary structure in the assembly (table 1) (ref 11 paper recomb biomaterials).
Depending on the processing of the silk proteins, it can have a degree of these secondary structures, defining its properties (table 1). This characteristic of the silk proteins will be discussed in detail in the ‘Silk protein’(link) section.
| Amino acid sequence | Secondary structure | Properties |
|---|---|---|
| AAAAAAAA | β-sheet | Tensile strenght, rigidity, hydrophobicity |
| GPG(AG)QQ / GPG(SGG)QQ / GPGGX | β-spiral / β-turn | Extensibility, elasticity |
| GGX | 310 helix | Link, alignment, flexibility |
In order to make the silk material a large amount of these proteins are required. The protein has a very repetitive nature (fig. 2), with these motifs (table 1) recurring within the protein. This is difficult to produce, because it requires presence of the same tRNAs in a large amount. This can be solved with codon optimization. See ‘Codon optimization’ (link) at the modelling section for the explanation of this approach.
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| Figure 2, Major ampullate Spidroin 2 (MaSp2) from Argiope aurantia |
