Mechanism of sulfur transfer across protein-protein interfaces: The cysteine desulfurase model system
CsdA cysteine desulfurase (the sulfur donor) and the CsdE sulfur acceptor are involved in biological sulfur trafficking and in iron-sulfur cluster assembly in the model bacterium Escherichia coli. CsdA and CsdE form a stable complex through a polar interface that includes CsdA Cys328 and CsdE Cys61,...
| Autores: | , , , , , , , , , , , , |
|---|---|
| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2016 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/142034 |
| Acceso en línea: | http://hdl.handle.net/10261/142034 |
| Access Level: | acceso abierto |
| Sumario: | CsdA cysteine desulfurase (the sulfur donor) and the CsdE sulfur acceptor are involved in biological sulfur trafficking and in iron-sulfur cluster assembly in the model bacterium Escherichia coli. CsdA and CsdE form a stable complex through a polar interface that includes CsdA Cys328 and CsdE Cys61, the two residues known to be involved in the sulfur transfer reaction. Although mechanisms for the transfer of a sulfur moiety across protein-protein interfaces have been proposed based on the IscS-IscU and IscS-TusA structures, the flexibility of the catalytic cysteine loops involved has precluded a high resolution view of the active-site geometry and chemical environment for sulfur transfer. Here, we have used a combination of X-ray crystallography, solution NMR and SAXS, isothermal calorimetry, and computational chemistry methods to unravel how CsdA provides a specific recognition platform for CsdE and how their complex organizes a composite functional reaction environment. The X-ray structures of persulfurated (CsdA) and persulfurated (CsdA-CsdE) complexes reveal the crucial roles of the conserved active-site cysteine loop and additional catalytic residues in supporting the transpersulfuration reaction. A mechanistic view of sulfur transfer across protein-protein interfaces that underpins the requirement for the conserved cysteine loop to provide electrostatic stabilization for the in-transfer sulfur atom emerges from the analysis of the persulfurated (CsdA-CsdE) complex structure. |
|---|