A conserved spider silk domain acts as a molecular switch that controls fibre assembly.
A huge variety of proteins are able to form fibrillar structures, especially at high protein concentrations. Hence, it is surprising that spider silk proteins can be stored in a soluble form at high concentrations and transformed into extremely stable fibres on demand. Silk proteins are reminiscent of amphiphilic block copolymers containing stretches of polyalanine and glycine-rich polar elements forming a repetitive core flanked by highly conserved non-repetitive amino-terminal and carboxy-terminal domains. The N-terminal domain comprises a secretion signal, but further functions remain unassigned. The C-terminal domain was implicated in the control of solubility and fibre formation initiated by changes in ionic composition and mechanical stimuli known to align the repetitive sequence elements and promote beta-sheet formation. However, despite recent structural data, little is known about this remarkable behaviour in molecular detail. Here we present the solution structure of the C-terminal domain of a spider dragline silk protein and provide evidence that the structural state of this domain is essential for controlled switching between the storage and assembly forms of silk proteins. In addition, the C-terminal domain also has a role in the alignment of secondary structural features formed by the repetitive elements in the backbone of spider silk proteins, which is known to be important for the mechanical properties of the fibre.
Hagn
Franz
F
Center for Integrated Protein Science (CIPSM), Technische Universität München, 85747 Garching, Germany.
Eisoldt
Lukas
L
Hardy
John G
JG
Vendrely
Charlotte
C
Coles
Murray
M
Scheibel
Thomas
T
Kessler
Horst
H
D000818:Animals; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D017124:Conserved Sequence; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D047011:Silk / Q000737:chemistry* / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D013112:Spiders / Q000737:chemistry*
D047011:Silk
Angew Chem Int Ed Engl. 2009;48(20):3584-96
19212993
Biointerphases. 2009 Sep;4(3):43-6
20408722
J Biomol NMR. 1999 Oct;15(2):177-80
20872110
Angew Chem Int Ed Engl. 2007;46(19):3559-62
17397124
J Biol Chem. 1994 Sep 30;269(39):24354-60
7929094
Anal Biochem. 2006 Oct 15;357(2):289-98
16962548
Int J Biol Macromol. 2000 Jun 13;27(3):205-10
10828366
Biochem Soc Trans. 2009 Aug;37(Pt 4):677-81
19614574
Biochemistry. 2004 Oct 26;43(42):13604-12
15491167
J Am Chem Soc. 2009 Mar 25;131(11):3794-5
19292479
J Mol Biol. 2001 Jun 15;309(4):949-60
11399071
Biochem Biophys Res Commun. 2005 Dec 16;338(2):897-902
16253207
J Magn Reson. 2003 Jan;160(1):65-73
12565051
Biomacromolecules. 2008 Sep;9(9):2399-407
18702545
Biomacromolecules. 2006 Jun;7(6):1790-5
16768399
J Biomol NMR. 1999 Mar;13(3):289-302
10212987
Biomacromolecules. 2005 Nov-Dec;6(6):3152-9
16283740
J Biomol NMR. 1991 Sep;1(3):299-304
1841700
J Exp Biol. 1999 Dec;202(Pt 23):3295-303
10562512
Adv Protein Chem. 1979;33:167-241
44431
Nature. 2003 Aug 28;424(6952):1057-61
12944968
Nature. 2001 Mar 29;410(6828):541-8
11279484
Trends Biochem Sci. 1996 Oct;21(10):375-82
8918191
Int Arch Allergy Immunol. 1995 Aug;107(4):484-90
7620364
Nature. 2003 Dec 18;426(6968):884-90
14685248
J Biomol NMR. 1995 Nov;6(3):306-12
8520222
J Mol Biol. 2002 Nov 22;324(2):309-18
12441109
Biomacromolecules. 2006 Nov;7(11):3120-4
17096540
Naturwissenschaften. 2001 Apr;88(4):179-82
11480706
Proc Natl Acad Sci U S A. 2009 Jun 2;106(22):8906-11
19458259
Proc Natl Acad Sci U S A. 2008 May 6;105(18):6590-5
18445655