1KAQ: Structure Of Bacillus Subtilis Nicotinic Acid Mononucleotide Adenylyl Transferase

The nadD gene, encoding the enzyme nicotinic acid mononucleotide (NaMN) adenylyltransferase (AT), is essential for the synthesis of NAD and subsequent viability of the cell. The nadD gene in Bacillus subtilis (yqeJ) was identified by sequence homology with other bacterial nadD genes and by biochemical characterization of the gene product. NaMN AT catalyzes the reversible adenylation of both NaMN and the nicotinamide mononucleotide (NMN) but shows specificity for the nicotinate. In contrast to other known NMN ATs, biophysical characterizations reveal it to be a dimer. The NaMN AT crystal structure was determined for both the apo enzyme and product-bound form, to 2.1 and 3.2 A, respectively. The structures reveal a "functional" dimer conserved in both crystal forms and a monomer fold common to members of the nucleotidyl-transferase alpha/beta phosphodiesterase superfamily. A structural comparison with family members suggests a new conserved motif (SXXXX(R/K)) at the N terminus of an alpha-helix, which is not part of the shared fold. Interactions of the nicotinic acid with backbone atoms indicate the structural basis for specificity.
PDB ID: 1KAQDownload
MMDB ID: 20148
PDB Deposition Date: 2001/11/2
Updated in MMDB: 2014/11
Experimental Method:
x-ray diffraction
Resolution: 3.2  Å
Source Organism:
Similar Structures:
Biological Unit for 1KAQ: hexameric; determined by author and by software (PISA)
Molecular Components in 1KAQ
Label Count Molecule
Proteins (6 molecules)
Nicotinate-nucleotide Adenylyltransferase(Gene symbol: nadD)
Molecule annotation
Chemicals (6 molecules)
* Click molecule labels to explore molecular sequence information.

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