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Crystal structure of NH3‐dependent NAD+ synthetase from Bacillus subtilis.
Author(s) -
Rizzi M.,
Nessi C.,
Mattevi A.,
Coda A.,
Bolognesi M.,
Galizzi A.
Publication year - 1996
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1996.tb00896.x
Subject(s) - biology , genetics , library science , computer science
NAD+ synthetase catalyzes the last step in the biosynthesis of nicotinamide adenine dinucleotide. The three‐dimensional structure of NH3‐dependent NAD+ synthetase from Bacillus subtilis, in its free form and in complex with ATP, has been solved by X‐ray crystallography (at 2.6 and 2.0 angstroms resolution, respectively) using a combination of multiple isomorphous replacement and density modification techniques. The enzyme consists of a tight homodimer with alpha/beta subunit topology. The catalytic site is located at the parallel beta‐sheet topological switch point, where one AMP molecule, one pyrophosphate and one Mg2+ ion are observed. Residue Ser46, part of the neighboring ‘P‐loop’, is hydrogen bonded to the pyrophosphate group, and may play a role in promoting the adenylation of deamido‐NAD+ during the first step of the catalyzed reaction. The deamido‐NAD+ binding site, located at the subunit interface, is occupied by one ATP molecule, pointing towards the catalytic center. A conserved structural fingerprint of the catalytic site, comprising Ser46, is very reminiscent of a related protein region observed in glutamine‐dependent GMP synthetase, supporting the hypothesis that NAD+ synthetase belongs to the newly discovered family of ‘N‐type’ ATP pyrophosphatases.