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Figure 2.
Figure 2: Argos has three similar domains that resemble the
three-finger toxin fold of TGF- beta- receptors.
a, The overall fold of the three constituent domains in Argos
is illustrated with domain 3. The four strands (  1–
4)
form two fingers (fingers 1 and 2) that resemble those on a left
hand (as shown). The 'palm' side of the domain faces out of the
page. A knuckle-like protrusion projects below the page. At the
top of the domain is a disulphide-bonded core from which emanate
the two fingers plus the thumb (marked). Cysteine residues C1 to
C6, which make C1–C3, C2–C5 and C4–C6 disulphides, are
labelled, as are N and C termini. b, Domains 1, 2 and 3 are
overlaid (as C  ribbons)
in the same orientation used in a. Colours are as in Fig. 1.
Strand 1',
unique to domain 1, is labelled, as is the location of the 120
residue insert (Ins.) removed to generate Argos[217]. Two
orthogonal views are shown. c, Domain 3 of Argos (red) overlaid
with the 100-residue extracellular ligand-binding domain (ECD)
of the type II activin receptor (ActRII)^14 (coloured light
grey; from Protein Data Bank code 2GOO).
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