Science - USA (2022-01-14)

large number of unambiguous intra- and inter-
molecular solid-state NMR distance restraints,
are most similar to those of type I Ab42 fila-
ments (Fig. 4C) ( 31 ).
Reconstructions of type I and type II fila-
ments show strong densities for residues 41

and 42, which indicates that most molecules

correspond to Ab42. In agreement, immuno-

blotting (fig. S4) and mass spectrometry (fig.

S5) of extracted filaments showed that Ab 42

was the most abundant species in all cases,

with variable amounts of Ab40.

We performed immunohistochemistry on

the contralateral sides of the brain regions

used for cryo-EM, immunoblotting, and mass

spectrometry (figs. S6 and S7). Deposits of

Ab42 were also more numerous than those

of Ab40, with sporadic Alzheimer’s disease

170 14 JANUARY 2022•VOL 375 ISSUE 6577 science.orgSCIENCE

Fig. 3. Protofilament folds
and putative metal ionÐ
binding sites of type I
and type II Ab42 fila-
ments.(A) Superposition of
the structures of F20-V24
arcs overlaid on the
corresponding section
of the 2.5-Å electron density
map of type I filaments.
Putative metal ions are
shown as teal and purple
spheres. (BandC) Side
views of putative metal ionÐ
binding sites in type I
(teal) and type II (purple)
protofilaments, superimposed
on the corresponding
density maps. (D) Superpo-
sition of type I (orange) and
type II (blue) protofila-
ments, based on the central
layer of their S-shaped
domains. (EandF) Side
views of type I (E) and type II
(F) protofilaments along
the centralb3 strand. The center layer monomers in five successive rungs are shown in cartoon, withbstrands shown as arrows.

S26

G37

G25

G9

F19

F20

F19

F20

V12

A42

V36

E22 E22 D23

D23

ABC

E22 D23

DEF

C

C

β 3 β^3

Fig. 4. Comparison of protofilaments and
filaments of brain Ab42 with those of
seeded recombinant Ab40, recombinant
Ab42, and recombinant Ab 40 DE22.
(A) Comparison of the cryo-EM structures
of human brain type I and type II Ab 42
protofilaments with the cryo-EM structure of
seeded recombinant Ab40 protofilaments.
Type I is shown in orange, type II is in blue, and
seeded Ab40 [Protein Data Bank (PDB) ID
6W0O] is in gray. (B) Comparison of cryo-EM
structures of human brain type I and type II
protofilaments with cryo-EM and NMR
structures of recombinant protofilaments.
PDB IDs and color codes for recombinant Ab 42
filaments are as follows: 5OQV, wheat; 2NAO,
dark gray; 2MXU, gray; and 5KK3, light gray.
(C) Comparison of cryo-EM structures of
human brain type I filaments and NMR
structures of recombinant Ab 40 DE22
filaments. Human brain type I is shown in
orange, recombinant Ab 40 DE22 (PDB 2MVX)
is in gray, and residues aroundDE22 are
shown in green. (D) Comparison of cryo-EM
structures of Ab42 filaments from the brains of
mouse knock-in lineAppNL-Fwith human brain type II filaments. Mouse brain filaments are in green, and human brain type II filaments are in blue.

G9

A42

D1

E22

V40

D23

A21

V40

Y10

D1

A42/A42

G9

V12

A

C

B

A42

G9

Q15

E11

E11

V12

A42

V12/V12

D

G37

G25

A42

A42 V12/V12

A42

V40 D1

A42

H14

G9

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