PMID:15835909
| Citation |
Shan, SO and Walter, P (2005) Molecular crosstalk between the nucleotide specificity determinant of the SRP GTPase and the SRP receptor. Biochemistry 44:6214-22 |
|---|---|
| Abstract |
In signal recognition particle (SRP)-dependent targeting of proteins to the bacterial plasma membrane, two GTPases, Ffh (the SRP GTPase) and FtsY (the receptor GTPase), form a complex in which both proteins reciprocally stimulate each other's GTPase activities. We mutated Asp251 in the Ffh active site to Asn (D251N), converting Ffh to a xanthosine 5'-triphosphate (XTP)-specific protein as has been observed in many other GTPases. Unexpectedly, mutant SRP(D251N) is severely compromised in the formation of an active SRP.FtsY complex when bound with cognate XTP, and even more surprisingly, mutant SRP(D251N) works better when bound with noncognate GTP. These paradoxical results are explained by a model in which Ffh Asp251 forms a bidentate interaction with not only the bound GTP but also the receptor FtsY across the dimer interface. These interactions form part of the network that seals the lateral entrance to the composite active site at the dimer interface, thereby ensuring the electrostatic and/or structural integrity of the active site and contributing to the formation of an active SRP.FtsY complex. |
| Links |
PubMed Online version:10.1021/bi0500980 |
| Keywords |
Amino Acid Substitution; Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Catalytic Domain/genetics; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Kinetics; Models, Molecular; Mutagenesis, Site-Directed; Protein Conformation; Receptor Cross-Talk; Receptors, Cytoplasmic and Nuclear/chemistry; Receptors, Cytoplasmic and Nuclear/genetics; Receptors, Cytoplasmic and Nuclear/metabolism; Recombinant Proteins/chemistry; Recombinant Proteins/genetics; Recombinant Proteins/metabolism; Signal Recognition Particle/chemistry; Signal Recognition Particle/genetics; Signal Recognition Particle/metabolism |
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