Cleavage of nicotinamide adenine dinucleotide by the ribosome-inactivating protein from Momordica charantia.
The interaction of momordin, a type 1 ribosome-inactivating protein from Momordica charantia, with NADP(+) and NADPH has been investigated by X-ray diffraction analysis of complexes generated by co-crystallization and crystal soaking. It is known that the proteins of this family readily cleave the adenine-ribose bond of adenosine and related nucleotides in the crystal, leaving the product, adenine, bound to the enzyme active site. Surprisingly, the nicotinamide-ribose bond of oxidized NADP(+) is cleaved, leaving nicotinamide bound in the active site in the same position but in a slightly different orientation to that of the five-membered ring of adenine. No binding or cleavage of NADPH was observed at pH 7.4 in these experiments. These observations are in accord with current views of the enzyme mechanism and may contribute to ongoing searches for effective inhibitors.
Astex Therapeutics, 436 Cambridge Science Park, Milton Road, Cambridge CB4 0QA, England.
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M
Vinkovic
School of Biological Science, University of Southampton, Highfield, Southampton SO16 7PX, England.
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G
Dunn
Poole Hospital NHS Foundation Trust, Longfleet Road, Poole BH15 2JB, England.
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GE
Wood
Department of Crystallography, Birkbeck College, Malet Street, London WC1E 7HX, England.
J
J
Husain
Laboratory of Protein Crystallography, Centre for Amyloidosis and Acute Phase Proteins, UCL Division of Medicine (Royal Free Campus), Rowland Hill Street, London NW3 2PF, England.
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SP
Wood
Laboratory of Protein Crystallography, Centre for Amyloidosis and Acute Phase Proteins, UCL Division of Medicine (Royal Free Campus), Rowland Hill Street, London NW3 2PF, England.
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R
Gill
D003460:Crystallization; D018360:Crystallography, X-Ray; D029777:Momordica charantia / Q000737:chemistry*; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000737:chemistry* / Q000378:metabolism*; D010936:Plant Extracts / Q000737:chemistry; D017433:Protein Structure, Secondary; D054788:Ribosome Inactivating Proteins / Q000737:chemistry* / Q000378:metabolism*; D055672:Static Electricity
D010936:Plant Extracts; C548297:momordin; D009243:NAD; D009249:NADP; D054788:Ribosome Inactivating Proteins
N-glycosidase; crystal structure; momordin; nicotinamide; ribosome-inactivating protein