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Title
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Comparison of the three-dimensional protein and nucleotide structure of the FAD-binding domain of p-hydroxybenzoate hydroxylase with the FAD- as well as NADPH-binding domains of glutathione reductase.
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Authors
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R.K.Wierenga,
J.Drenth,
G.E.Schulz.
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Ref.
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J Mol Biol, 1983,
167,
725-739.
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PubMed id
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Abstract
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The chain fold of the FAD-binding domain of p-hydroxybenzoate hydroxylase
resembles the chain folds of the two nucleotide-binding domains of glutathione
reductase. This fold consists of a four-stranded parallel beta-sheet sandwiched
between a three-stranded antiparallel beta-sheet and alpha-helices. The
nucleotides bind in similar positions relative to this chain fold. The best
superposition of the folds has been established and geometrically quantified,
giving rise to an equivalencing scheme for 110 residue positions, of which only
four residues are identical in all three domains. It is discussed whether this
chain fold is also present in a number of other FAD-binding proteins with known
sequence. After the second strand of the parallel beta-sheet both FAD-binding
domains contain long chain excursions, which make intimate contacts to rather
distant parts of the respective molecules. In the environment of the
isoalloxazine rings we observe interesting similarities. In both enzymes the
si-face of this ring is covered by polypeptide, and only the re-face is
accessible for the cofactor NADPH. Furthermore, there is a long alpha-helix in
each enzyme, which points with its N-terminal start to the O-2 alpha region of
isoalloxazine. These helices are spatially in the same position with respect to
the isoalloxazine ring but are at quite different positions along the
polypeptide chain. Since they can stabilize a negative charge around O-2 alpha,
they may be important for the catalytic processes.
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