|
 |
|
|
| The EMBO Journal
(2001) 20, 6724–6734, doi:10.1093/emboj/20.23.6724 |
|
| Evidence for a novel GTPase priming step in the SRP protein targeting pathway |
|
|
| Yun Lu1, Hai-Yan Qi1, Janine B. Hyndman1, Nancy D. Ulbrandt2, Alexey Teplyakov3, Nenad Tomasevic1 and Harris D. Bernstein1 |
|
|
1 Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 10, Room 9D-20, Bethesda, MD 20892-1810, USA 2 Present address: Medimmune, Inc., Gaithersburg, MD 20878, USA 3 Center for Advanced Research in Biotechnology, 9600 Gudelsky Drive, Rockville, MD 20850, USA To whom correspondence should be addressed Harris D. Bernstein, harris_bernstein@nih.gov Received 23 August 2001; Revised 4 October 2001; Accepted 10 October 2001. |
|
|
|
| Abstract |
|
Protein targeting by the signal recognition particle (SRP) pathway requires the interaction of two homologous GTPases that reciprocally regulate each other's GTPase activity, the SRP signal peptide- binding subunit (SRP54) and the SRP receptor  -subunit (SR). The GTPase domain of both proteins abuts a unique 'N domain' that appears to facilitate external ligand binding. To examine the relationship between the unusual regulation and unique architecture of the SRP pathway GTPases, we mutated an invariant glycine in Escherichia coli SRP54 and SR orthologs ('Ffh' and 'FtsY', respectively) that resides at the N–GTPase domain interface. A G257A mutation in Ffh produced a lethal phenotype. The mutation did not significantly affect Ffh function, but severely reduced interaction with FtsY. Likewise, mutation of FtsY Gly455 produced growth defects and inhibited interaction with Ffh. The data suggest that Ffh and FtsY interact only in a 'primed' conformation which requires interdomain communication. Based on these results, we propose that the distinctive features of the SRP pathway GTPases evolved to ensure that SRP and the SR engage external ligands before interacting with each other. |
|
| Keywords: GTPase, protein targeting, SRP, SRP receptor |
|
|
| |
| |
| |
 | 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 | |
| |
| |
| |
