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Figure 3.
Fig. 3. Structural comparison between PGRP-bound PGN
analogs in crystal structures and unbound GMPP[2] in solution.
(A) Conformational comparison of GMPP, MPP, TCT, and GMPP[2].
GMPP, MPP, and TCT are from crystal structures of complexes with
human PGRP-I  C, human PGRP-I  C (16),
and Drosophila PGRP-LE (27), respectively; GMPP[2] is from the
unliganded NMR structure (17). The structures are superposed
through the pyranose ring of NAM (for MPP, GMPP, and GMPP[2]) or
NAM(1,6-anhydro) (for TCT). (B) Superposition of unbound GMPP[2]
onto GMPP in the PGRP-I C–GMPP complex. GMPP
and GMPP[2] are shown in ball-and-stick representations, with
carbon atoms in yellow and green, respectively, nitrogen atoms
in blue, and oxygen atoms in red. Of the two GMPP units in
GMPP[2], the first unit, comprising the NAG[1]-NAM[1]
disaccharide, is superposed onto GMPP in the complex. The
peptide stem of GMPP[2] attached to NAM[1] is buried within
PGRP-I C and is shown in pale
green. (C) Alternative superposition of unliganded GMPP[2] onto
GMPP bound to PGRP-I C. In this case, the
second GMPP unit of GMPP[2], containing NAG[2]-NAM[2], is
superposed onto GMPP in the PGRP-I C–GMPP structure. The
peptide stem of GMPP[2] attached to NAM[2], shown in pale green,
is buried inside PGRP-I C. (D) Modeled PGRP-I
C–GMPP[2] structure.
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