Crystal Structure of a Complex Between the Phosphorelay Protein YPD1 and the Response Regulator Domain of SLN1 Bound to a Phosphoryl Analog
The crystal structure of the yeast SLN1 response regulator (RR) domain bound to both a phosphoryl analog [beryllium fluoride (BeF3 -)] and Mg2 +, in complex with its downstream phosphorelay signaling partner YPD1, has been determined at a resolution of 1.70 Angstroms. Comparisons between the BeF3 --activated complex and the unliganded (or apo) complex determined previously reveal modest but important differences. The SLN1-R1{center_dot}Mg2 +{center_dot}BeF3 - structure from the complex provides evidence for the first time that the mechanism of phosphorylation-induced activation is highly conserved between bacterial RR domains and this example from a eukaryotic organism. Residues in and around the active site undergo slight rearrangements in order to form bonds with the essential divalent cation and fluorine atoms of BeF3 -. Two conserved switch-like residues (Thr1173 and Phe1192) occupy distinctly different positions in the apo versus BeF3 --bound structures, consistent with the 'Y-T' coupling mechanism proposed for the activation of CheY and other bacterial RRs. Several loop regions and the a4-{beta}5-a5 surface of the SLN1-R1 domain undergo subtle conformational changes ({approx} 1-3 Angstroms displacements relative to the apo structure) that lead to significant changes in terms of contacts that are formed with YPD1. Detailed structural comparisons of protein-protein interactions in the apo and BeF3 --bound complexes suggest at least a two-state equilibrium model for the formation of a transient encounter complex, in which phosphorylation of the RR promotes the formation of a phosphotransfer-competent complex. In the BeF3 --activated complex, the position of His64 from YPD1 needs to be within ideal distance of and in near-linear geometry with Asp1144 from the SLN1-R1 domain for phosphotransfer to occur. The ground-state structure presented here suggests that phosphoryl transfer will likely proceed through an associative mechanism involving the formation of a pentacoordinate phosphorus intermediate.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 959744
- Report Number(s):
- BNL-82730-2009-JA; JMOBAK; TRN: US1005796
- Journal Information:
- Journal of Molecular Biology, Vol. 375, Issue 4; ISSN 0022-2836
- Country of Publication:
- United States
- Language:
- English
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