Under construction. Last update March 28 1995
P-pilus chaperone PapD binding cleft mutant R8A
R8A forms a dimer that may represent an important uncapping
intermediate
A deep celft is formed between the two immunglobulin domains of
PapD. At the bottom of the cleft a number
of conserved residues are found that are critical for chaperone function.
One of these residues, Arg 8, is involved in binding the C-terminus of the
pilus subunits. Mutations of Arg 8 renders the chaperone incapaple of
supporting pilus assembly. The structure of the Arg 8 to Ala mutation has been
solved and is currently being refined. The mutant crystallizes as a dimer that
may represent an important intermediate in the capping/uncapping process at
the usher during pilus assembly. The two subunits of the dimer interact
primarily through their G1 strands which bind as antiparallel strands. Further
interactions are mediated through flexible loop regions at the tips of the
domains. Phe 168 in the FG loop of one subunit binds in a well define pocket
on the surface of the second subunit in the dimer.
Stefan Knight
Swedish University of Agricultural Sciences
Uppsala Biomedical Centre
Department of Molecular Biology
P.O. Box 590
S-751 24 Uppsala
Sweden
stefan@xray.bmc.uu.se
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