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Figure 5.
Figure 5. The Integrin Cycle
(A) In the bent
conformation, integrins have low affinity for ligand.
(B)
At sites where actin filaments are formed, the integrin β
subunit cytoplasmic domain binds through talin or kindlins.
Lateral translocation on the cell surface and buffeting cause
integrin extension. Both open and closed headpiece conformations
are putatively present.
(C) Binding to an immobilized
extracellular ligand greatly increases the lateral force and
markedly favors the high-affinity, open headpiece conformation.
(D) Disassembly of the actin cytoskeleton removes the
lateral force. Tensile force between the ligand and the integrin
cytoplasmic domains favors the closed headpiece conformation and
ligand dissociation.
(E) Ligand dissociates, further
favoring the closed headpiece conformation.
(F) In the
absence of ligand and tensile force, the bent conformation is
favored, completing the cycle, and the integrin returns to the
same state as shown in (A).
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