Crystal Structure of Escherichia coli ATase N-terminal domain

Yibin Xu,^a Rongguang Zhang,^b Paul D. Carr,^c David L. Ollis,^c and Subhash G.Vasudevan^a,d

^aDepartment of Biochemistry & Molecular Biology, James Cook University, Townsville, QLD 4811; ^bStructural Biology Centre, Argonne National Laboratory, USA; ^cResearch School of Chemistry, Australian National Univeristy, Canberra, ACT 2601; ^dPresent address: Novartis Institute for Tropical Diseases, 1 Science Park Road, #04-14 The Capricorn, Singapore (yibin.xu@jcu.edu.au)

E.coli glutamine synthetase adenylyltransferase (ATase, EC 2.7.7.42) catalyses the adenylylation and deadenylylation of glutamine synthetase (GS). The two activities of ATase are mechanistically distinct, but are functionally the reverse of one another and must be carefully controlled by the organism in order to prevent futile cycling. Growth will occur in a low ammonia environment if GS is active with the deadenylylation activity of ATase switched on and the adenylylation activity switched off. Conversely, in a high ammonia environment, GS activity can be tuned down progressively by adenylylation until it is completely switched off when all 12 subunits are converted to the inactive GS-AMP form. It has been shown that two activities of ATase reside on separate domains. AT-N consisted of residues 1 through to 423 and was found to have the deadenylylation activity but only partially soluble [1]. However ATN440 (residues 1 to 440) is soluble and here we report the purification, crystallization and 3D structure determination of AT-N 440.

The crystals of ATN-440 belong to space group P3₂21 with a=b= 116.6 Å, c=67.6 Å, a=b=90° and g=120°. Its crystal structure has been determined by the MAD method and refined up to a resolution of 2.0 Å. The structure reveals a conserved protein motif present also in kanamycin nucleotidylyltransferase and human DNA polymerase b.

References

1 Jaggi, R., van Heeswijk, W. C., Westerhoff, H.V., Ollis, D.L. and Vasudevan, S.G. (1997). EMBOJ 16, 5562-5571.