The World of Functional Amyloid - The Functional Fold: Amyloid Structures in Nature - page 3

to the fibre axis. The molecular structure of amyloid fibres has been
extensively studied using numerous biophysical techniques for more
than 40 years.

a b

c

Figure 1.1 Amyloid fibres have a cross- -sheet fold. Amyloid is a fibrous

protein quaternary structure. (a) A transmission electron
micrograph of negatively stained amyloid fibres formed from
full length IAPP (reprinted with permission from Wiley-Liss,
Inc., a subsidiary of John Wiley & Sons, Inc.; from Stromer

β

et

al . 4 ). Higher magnifications (lower panels) reveal twisted rope

and sheet like arrangements of individual protofilaments.
(b) An X-ray fibre diffraction pattern from partially aligned
A

β (1 42)

amyloid fibres associated with Alzheimer disease
exhibiting the characteristic reflections at 4.7 and ≈10 Å
(reprinted with permission of Wiley-Liss, Inc., a subsidiary of
John Wiley & Sons, Inc., from Stromer

-

. 4 ). The meridional
reflection at 4.7 Å results from the inter-strand repeats and the
≈10 Å equatorial reflection arises from inter-sheet packing.
(c) A

et al

β

(1-42) fibre structure obtained from solid-state NMR
techniques and complementation mutagenesis methodology 5,6
reveals the characteristic cross- -sheet amyloid structure

(PDB ID 2BEG). Molecular graphics were produced with Pymol
(DeLano, W.L. The PyMOL Molecular Graphics System (2002)
on World Wide Web, http://www.pymol.org). See also Colour
Insert.

β