Biology Reference
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12,31
of the cA peptide.
Its sequence shows structural similarities
with the sequence of UDP-N-acetylglucosamine acyltransferase
(Fig. 4.12a), and the peptide would have a hydrophobic core when
b
c
a
Figure 4.12
(a) Alignment of the sequence of the cA peptide with the
sequenceoftheN-terminaldomainofUDP-N-Acetylglucosamine
Acyltransferase (LpxA of
Escherichia
coli
) [Raetz, C. R. H. and
Roderick, S. R. (1995)
, 997-1000]. The one letter
code is used. Sequences should be read continuously beginning
at the top. The structure of the N-terminal domain of LpxA
of
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270
E. coli
is a left-handed parallel
β
-helix [Raetz, C. R. H. and
Roderick, S. R. (1995)
, 997-1000]. C1 to C10 rows
identify individual turns of the helix. PB1, PB2, and PB3 denote
the parallel
Science
270
-strands of each turn. T1, T2, and T3 denote turn
residues. Conserved hydrophobic residues, which have their
side-chains pointing towards the interior of the left-handed
parallel
β
β
-helix to form the hydrophobic core, are black boxed.
(b) A representation of the electrostatic surface potential of
the left-handed parallel
-helix model, derived by homology
modelling for the cA peptide, from the alignment shown in
(a) (Iconomidou
β
., 2000), calculated by the program
DELPHI and displayed using GRASP (Nicholls
et al
et al
., 1991;
Nicholls, 1993). The calculations were performed with the
default charges file. Electrostatic potential is shown from
-10 kT (red) to +10 kT (blue). (c) A ribbon model of the left-
handed parallel
-helix model for the cA peptide, derived
as described in (b), displayed using GRASP (Nicholls
β
et al.,
1991). Tentative type II
β
-turns alternate with four-residue
β
-strands. The side chains of the residues and the carbonyl
oxygens of the main chain are shown as “sticks”. View almost
parallel to the axis of the left-handed parallel
β
-helix. See also
Colour Insert.
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