Mammalian Functional Amyloid - The Functional Fold: Amyloid Structures in Nature - page 153

a

b c

Figure 9.3 Pmel fibres accelerate melanin synthesis. ( ) In melanosomes,

assembly of activated melanin precursors, generated by
tyrosinase, occurs along Pmel17 fibres. The boxed portion of
(a) illustrates the amyloid-binding dye thioflavin T and the
activated melanin precursor 5,6-indolequinone (DHQ), which
possess similar core structures. This suggests an explanation
for the ability of Pmel17 to concentrate and organize melanin
precursors, thereby enabling melanogenesis. (b) A time course
of melanin synthesis

a

shows that insoluble rMα amyloid
increases the amount of insoluble melanin formed per unit
time (grey line) versus a control reaction lacking rMα (black
line). (c) Melanin synthesis after 20 h was also evaluated in
the presence of insoluble rMα amyloid, α-synuclein amyloid,
Aβ amyloid, and collagen IV α-helical fibres. Amyloid fibres,
regardless of the component protein, are able to enhance
melanin synthesis. Reproduced from Fowler

in vitro

. 5 See also

et al

Colour Insert.