Structural adaptation of an interacting non-native C-terminal helical extension revealed in the crystal structure of NAD(+) synthetase from Bacillus anthracis.McDonald, H.M., Pruett, P.S., Deivanayagam, C., Protasevich, I.I., Carson, W.M., DeLucas, L.J., Brouillette, W.J., Brouillette, C.G.
(2007) Acta Crystallogr.,Sect.D 63: 891-905
- PubMed: 17642516
- DOI: 10.1107/S0907444907029769
- Primary Citation of Related Structures:
- PubMed Abstract:
The crystal structures of NH(3)-dependent NAD+ synthetase from Bacillus anthracis as the apoenzyme (1.9 A), in complex with the natural catalytic products AMP and pyrophosphate (2.4 A) and in complex with the substrate analog adenosine 5'-(alpha,beta ...
The crystal structures of NH(3)-dependent NAD+ synthetase from Bacillus anthracis as the apoenzyme (1.9 A), in complex with the natural catalytic products AMP and pyrophosphate (2.4 A) and in complex with the substrate analog adenosine 5'-(alpha,beta-methylene)triphosphate (2.0 A) have been determined. NAD+ synthetase catalyzes the last step in the biosynthesis of the vitally important cofactor NAD+. In comparison to other NAD+ synthetase crystal structures, the C-terminal His-tagged end of the apoenzyme adopts a novel helical conformation, causing significant compensatory changes in the region. The structural accommodations observed in B. anthracis NAD+ synthetase are remarkable in the absence of adverse affects on enzyme activity. They also illustrate a rare example of the influence of a non-native C-terminal His-tag extension on the structure of a native protein. In contrast to the apoenzyme, when AMP and pyrophosphate or adenosine 5'-(alpha,beta-methylene)triphosphate are bound, the C-terminus adopts a conformation that allows ATP binding and overall the structure then resembles other NAD+ synthetase structures. The structures of NAD+ synthetase complexes from B. anthracis are compared with published X-ray crystal structures of the enzyme from B. subtilis, Escherichia coli and Helicobacter pylori. These comparisons support the novel observation that P1 and P2 loop ordering is not a consequence of crystal contacts but rather a consequence of intrinsic intramolecular interactions within the ordered subunit.
Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, Birmingham, AL 35294-4440, USA.