|
 |
|
|
| The EMBO Journal
(1997) 16, 5562–5571, doi:10.1093/emboj/16.18.5562 |
|
| The two opposing activities of adenylyl transferase reside in distinct homologous domains, with intramolecular signal transduction |
|
|
| Rene Jaggi1, Wally C. van Heeswijk2, Hans V. Westerhoff2, David L. Ollis3 and Subhash G. Vasudevan1 |
|
|
1 Department of Biochemistry and Molecular Biology, James Cook University, Townsville, Queensland 4811, Australia 2 Department of Microbial Physiology, Faculty of Biology, Free University, De Boelelaan 1087, NL-1081 HV Amsterdam, The Netherlands 3 Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia To whom correspondence should be addressed Subhash G. Vasudevan, subhash.vasudevan@jcu.edu.au Received 7 February 1997; Revised 27 June 1997. |
|
|
|
| Abstract |
|
Adenylyl transferase (ATase) is the bifunctional effector enzyme in the nitrogen assimilation cascade that controls the activity of glutamine synthetase (GS) in Escherichia coli. This study addresses the question of whether the two antagonistic activities of ATase (adenylylation and deadenylylation) occur at the same or at different active sites. The 945 amino acid residue ATase has been truncated in two ways, so as to produce two homologous polypeptides corresponding to amino acids 1–423 (AT-N) and 425–945 (AT-C). We demonstrate that ATase has two active sites; AT-N carries a deadenylylation activity and AT-C carries an adenylylation activity. Glutamine activates the adenylylation reaction of the AT-C domain, whereas  -ketoglutarate activates the deadenylylation reaction catalysed by the AT-N domain. With respect to the regulation by the nitrogen status monitor PII, however, the adenylylation domain appears to be dependent on the deadenylylation domain: the deadenylylation activity of AT-N depends on PII-UMP and is inhibited by PII. The adenylylation activity of AT-C is independent of PII (or PII-UMP), whereas in the intact enzyme PII is required for this activity. The implications of this intramolecular signal transduction for the prevention of futile cycling are discussed. |
|
| Keywords: Escherichia coli adenylyl transferase, flexible linker, intramolecular signal transduction, nucleotidyl transferase, PII protein |
|
|
| |
| |
| |
 | Email link to a friend |
| |
 | Download PDF |
| |
 | Full text |
| |
| |
| |
 | Next article |
| |
 | Previous article |
| |
 | Table of contents |
| |
| |
 | Rights and permissions |
| |
 | Reprints |
| |
| |
| |
 Register for table of contents by email | |
| |
| |
| |