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PDBsum entry 1e3a
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Antibiotic resistance
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PDB id
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1e3a
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Structure of a slow processing precursor penicillin acylase from escherichia coli reveals the linker peptide blocking the active-Site cleft.
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Authors
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L.Hewitt,
V.Kasche,
K.Lummer,
R.J.Lewis,
G.N.Murshudov,
C.S.Verma,
G.G.Dodson,
K.S.Wilson.
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Ref.
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J Mol Biol, 2000,
302,
887-898.
[DOI no: ]
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PubMed id
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Abstract
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Penicillin G acylase is a periplasmic protein, cytoplasmically expressed as a
precursor polypeptide comprising a signal sequence, the A and B chains of the
mature enzyme (209 and 557 residues respectively) joined by a spacer peptide of
54 amino acid residues. The wild-type AB heterodimer is produced by proteolytic
removal of this spacer in the periplasm. The first step in processing is
believed to be autocatalytic hydrolysis of the peptide bond between the
C-terminal residue of the spacer and the active-site serine residue at the N
terminus of the B chain. We have determined the crystal structure of a slowly
processing precursor mutant (Thr263Gly) of penicillin G acylase from Escherichia
coli, which reveals that the spacer peptide blocks the entrance to the
active-site cleft consistent with an autocatalytic mechanism of maturation. In
this mutant precursor there is, however, an unexpected cleavage at a site four
residues from the active-site serine residue. Analyses of the stereochemistry of
the 260-261 bond seen to be cleaved in this precursor structure and of the
263-264 peptide bond have suggested factors that may govern the autocatalytic
mechanism.
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Figure 1.
Figure 1. Cartoon of PGA showing the secondary structural
elements, a-helices and b-sheets. (a) Mature enzyme [McVey
1999]. (b) Precursor: the A domain is shown in green, the B
domain in blue and the linker peptide is in red. The N-terminal
nucleophilic serine residue is also drawn in yellow as a ball
and stick model. Figure 1, Figure 2, Figure 5 and Figure 7 were
created with the program BOBSCRIPT [Esnouf 1997].
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Figure 7.
Figure 7. Final 2F[o] -F[c] electron density for residues
Tyr260 to Met266, contoured at a level of 1s. The extent of the
structural rearrangement in the environment surrounding the
cleavage between Tyr260 and Pro261, some 8 Å apart, is
evident. The electron density for Pro261 is poorly defined and
consistent with some disorder and high thermal mobility
(B-factor of >40 Å2). The close hydrogen bond between the
precursor conformation of the Ser264 Og and Gly263 is shown as a
broken line. The rest of the precursor structure is depicted as
a C^a trace and coloured according to domain, as in Figure 1.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2000,
302,
887-898)
copyright 2000.
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Secondary reference #1
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Title
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Crystallization of a precursor penicillin acylase from escherichia coli.
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Authors
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L.Hewitt,
V.Kasche,
K.Lummer,
A.Rieks,
K.S.Wilson.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 1999,
55,
1052-1054.
[DOI no: ]
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PubMed id
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Figure 1.
Figure 1 A photomicrograph of crystals of penicillin acylase
Thr263Gly mutant precursor. The dimensions of the largest single
crystal were 0.2 × 0.05 × 0.02 mm.
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The above figure is
reproduced from the cited reference
with permission from the IUCr
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