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Figure 1.
Figure 1. X-ray structure (Baker et al., 1988) of the insu-
lin hexamer showing the symmetrical arrangement of
three dimers around a vertical 3-fold axis. The dimer
in front is shown schematically with helices and
b-strands, whereas the other two are in surface rep-
resentation, orange and green, respectively. The mono-
mer is composed of two polypeptide chains, the
A-chain (A1 to A21), which folds into a helix-loop-
helix motif, and the B-chain (B1 to B30) containing an
N-terminal arm, a central helix and a C-terminal
b-strand (flat arrow). B-Chain residues contribute to
the interface between monomers in the dimer including
an antiparallel b-sheet formed by the B-chain C termini
and side-chains of the central helices. The interface
between dimers involves a distinct set of protein-pro-
tein contacts and is mainly composed of residues in
the N-terminal part of the B-chain with contributions
from residues in the C-terminal A-chain helix and the
B-chain helix, i.e. B1, B2 and B4 from one dimer inter-
act with residues A13, A14, B1 and B16 to B20 of the
opposing dimer (see Baker et al., 1988, for details).
Three cystine bridges A6.A11, A7.B7, and A20.B19
are shown in yellow in stick representation. Figure of
molecule was produced using Insight (Molecular Simu-
lations Inc.).
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