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Title
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Crystal structure analysis of the tetragonal crystal form are preliminary molecular model of pig-heart citrate synthase.
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Authors
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G.Wiegand,
D.Kukla,
H.Scholze,
T.A.Jones,
R.Huber.
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Ref.
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Eur J Biochem, 1979,
93,
41-50.
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PubMed id
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Abstract
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The crystal structure of pig heart citrate synthase was analyzed at 0.35-nm
resolution. Chain tracing was possible and an initial molecular model
constructed. The dimensions of the dimer molecule (located on a crystallographic
diad) are 7.5 x 6.0 x 9.0 nm. The chain folding is characterized by the
predominance of helices and the absence of sheet structure. The electron density
accounts for 355 residues per monomer, so that about 80 residues must be
disordered in the crystal. The disordered segment in probably N-terminal. The
ordered part consists of two closely associated domains, a large domain with 300
residues and a C-terminal domain of 55 residues consisting of 3(anti)parallel
helices. The large domain is built from 12 helical segments, some of which are
buried in the interior of the molecule. Inhibitor binding studies with citrate
and CoA revealed citrate binding sites but showed no electron density for CoA.
It is suggested that CoA binds to the disordered, flexible N-terminal domain.
Experiments of limited proteolysis with trypsin showed that under conditions a
segment of Mr 9000 is cleaved off selectively. The remaining 35 000-Mr part is
dimeric.
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