Team:Newcastle/Spider silk


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Spider Silk

Background Info

World’s strongest spider silk comes from species of the genus Nephila
(The golden orb spider: the largest spider in this genus is Nephila maculata)
Its impressive web can be up to 6metres long and 2metres wide and last several years.
It has long been used by man; tribal people wrapped it around sticks to catch fish.
In a modern setting its uses are becoming more and more valuable from parachutes to bullet proof vests and in this
project as measure to help fix cracks in concrete.
Spider Web.jpg        Golden orb web.jpg
[Buy a Nephila]

Major Ampulate Spidroin Proteins

Spider silk is comparable in strength to carbon fibres
Highly structured at the nanometre scale – not good for synthetic materials
Repetitive structures- GXG motif
Glycine rich segments – hard and soft segments alternating
Hard= hydrogen bonding cross-linked crystallites (polyalanine) forming an amorphic beta sheet structure,
Soft= flexibility (Glycine rich)
Major protein from Nephila clavipes – MaSP1 tandem variants of
MaSP2 also has a repetitive structure – difference soft segment contains proline containing pentamers: The consensus repeat is _GPGGY GPGQQ.3GPSGPGS A8. Similar structure to Elastin – elastic properties of drag-line by the folding of pentamer structure.
In the spider – silk in 3 phases
1) Extremely viscous (withstand shear forces inside spider),
2) Liquid crystallite lower viscosity (near exit duct/glycine rich may be involved),
3) Insoluble fibre (result of dehydration and drawing).
MaSP1 and MaSP2 – Drag line
MaSP2- Glue silk only
Neither- Cocoon silk
Super contraction associated with pentamer motif when wet: low visco-elasticity
Mimic natural proteins or simplify – Mimic structural significance still uncertain for some sequences
DPB1- Optimised for B.subtilis
B.subtilis potential host as simple secretion system compared to yeast. Secretion has advantages over expression in E.coli however; insufficient proportion of protein was secreted by yeast.
Fahnestock, S. R., Yao, Z., & Bedzyk, L. a. (2000). Microbial production of spider silk pr}oteins. Journal of biotechnology, 74(2), 105-19. Retrieved from

Self Assembly and pH

Self assembly of Spider silk proteins is controlled by a pH sensitive relay.
A drop to pH 6.3 and shearing forces are believes to result in the hard form of spider silk.
Miniature spidroins (a few repeats 4repCT) form metre long fibres irrespective of pH.
Introduction of N-terminal domain from MASP1 (Euprosthenops australis)
to mini spidroins allows self assembly at pH 6.3 and delays aggregation above pH7.
Relay- like mechanism N terminal regulates assembly. pH 8 NT-mini spidroins for long firbes over days at pH 6 they form rapidly.
C-terminal domain promotes Silk formation by ordering the repetitive segments.
Askarieh, G. et al., 2010. Self-assembly of spider silk proteins is controlled by a pH-sensitive relay. Nature, 465(7295), 236-238. Available at: