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Figure 2.
Molecular features of I65–I70. (A) Structure-based sequence
alignment where orange and yellow represent >90% and >70%
sequence identity, respectively, across all Ig of the skeletal
tandem. Green indicates conserved hydrophobic positions. The EPP
motif, NxxG sequence in β-hairpin FG, and the BC loop are boxed
in black. To ease comparison, the E group in tight linkers is
given as the last residue of the preceding domain. A conserved
set of residues (KD at the CC′ region and Y at β-strand F)
responsible for the conformation of the CC′D loop
characteristic of this Ig type is boxed in blue. (B) Molecular
surface of I65–I70 colored according to sequence conservation
as in A. (C) I65–I66 long linker interface. The three inserted
residues are in dark gray. The conserved E is now an integral
part of the linker, whereas L, the last of the inserted
residues, has replaced it at the N terminus of the following Ig.
(D) I68–I69 interface representative of tight connections. The
transition motif EPP, an integral part of the N terminus of
I69, is in green. The conserved N residue from β-hairpin FG and
the T group from the BC loop are in yellow; their interactions
are conserved in all Ig constituents of I65–I70. Hydrogen
bonds are shown as dashed lines (experimental electron density
for both linkers is shown in SI Fig 6).
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