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PDBsum entry 1obt
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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 and activity of an active site substitution of ricin a chain.
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Authors
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P.J.Day,
S.R.Ernst,
A.E.Frankel,
A.F.Monzingo,
J.M.Pascal,
M.C.Molina-Svinth,
J.D.Robertus.
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Ref.
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Biochemistry, 1996,
35,
11098-11103.
[DOI no: ]
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PubMed id
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Abstract
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The A chain of ricin (RTA) is an N-glycosidase which inactivates ribosomes by
removing a single adenine base from a conserved region of rRNA. X-ray structures
and site-directed mutagenesis revealed that Arg 180 interacts with the target
adenine hydrogen bonding with N3. It may fully or partially protonate that atom
as part of the hydrolysis mechanism. Arg 180 was previously converted to His
(R180H) and shown to greatly reduce activity. Here R180H is shown to reduce
overall activity 500-fold against Artemia salina ribosomes. A 2.2 A crystal
structure reveals the mutation causes a rearrangement of the active site cleft,
with Tyr 80 moving to block access to the adenine recognition site. His 180
forms a strong aromatic interaction with Trp 211, Tyr 80, and Tyr 123. A complex
is formed with 250 mM AMP. The nucleotide binds in the active site region, but
in an apparently nonproductive orientation. His 180 cannot bond to N3 and is
screened from the substrate analog by the intervening Tyr 80. It may be that
natural polynucleotide substrates, using additional interactions, can displace
Tyr 80 and effect a productive binding.
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Secondary reference #1
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Title
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X-Ray structure of recombinant ricin a-Chain at 1.8 a resolution.
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Authors
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S.A.Weston,
A.D.Tucker,
D.R.Thatcher,
D.J.Derbyshire,
R.A.Pauptit.
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Ref.
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J Mol Biol, 1994,
244,
410-422.
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PubMed id
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Secondary reference #2
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Title
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Structure of recombinant ricin a chain at 2.3 a.
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Authors
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D.Mlsna,
A.F.Monzingo,
B.J.Katzin,
S.Ernst,
J.D.Robertus.
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Ref.
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Protein Sci, 1993,
2,
429-435.
[DOI no: ]
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PubMed id
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Figure 2.
Fig. 2. Superposition of the refined
models of ricin Aand rRTA. Recom-
binant RTA, as refinedin this study is
shown in the heavy ondsasa Ca
trace. The refined ricin A chain (Ru-
tenber et al., 1991) is shown in thin
bonds.
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Figure 5.
Fig. 5. The active site of ricin. The conforma-
of ricin A is shown in light bonds and that
f rRTA n heavy bonds.
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The above figures are
reproduced from the cited reference
which is an Open Access publication published by the Protein Society
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