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Figure 1.
Fig. 1. Organization and overall structure of the synthetase
SrfA-C, the termination module of the surfactin biosynthesis
cluster from B. subtilis ATCC 21332. (A) The surfactin
biosynthetic operon [including srfA-A, 10,767 base pairs (bp);
srfA-B, 10,764 bp; srfA-C, 3825 bp] encoding the nonribosomal
peptide synthetases SrfA-A, B, and C and associated genes
(srfA-D and sfp). The chemical structure of the lipoheptapeptide
product surfactin is shown on the right. The yellow box
indicates the ring closure site between Leu^7 and the
β-hydroxyl group of the fatty acid catalyzed by SrfA-C. (B)
Schematic illustration of the terminal synthetase SrfA-C
comprising the condensation domain (C, gray), adenylation domain
(A, red and orange), peptidyl carrier protein domain (PCP,
green), and thioesterase domain (TE, brown). Linkers are blue;
the C-terminal tag helix is yellow. (C) Overall structure of
SrfA-C at 2.6 Å resolution. The C domain's catalytically
active residue His^147 and a leucine residue bound in the A
domain's active site are shown in space-filling representation.
Coloring of the domains is according to (B). See fig. S6 for
stereoviews of the total SrfA-C structure. All figures were made
with PYMOL 1.0 (20).
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