Demonstration of a multistep mechanism for assembly of the SRP x SRP receptor complex: implications for the catalytic role of SRP RNA.

ABSTRACT: Two GTPases in the signal recognition particle (SRP) and its receptor (SR) control the delivery of newly synthesized proteins to the endoplasmic reticulum or plasma membrane. During the protein targeting reaction, the 4.5S SRP RNA accelerates the association between the two GTPases by 400-fold. Using fluorescence resonance energy transfer, we demonstrate here that formation of a stable SRP x SR complex involves two distinct steps: a fast initial association between SRP and SR to form a GTP-independent early complex and then a GTP-dependent conformational rearrangement to form the stable final complex. We also found that the 4.5S SRP RNA significantly stabilizes the early GTP-independent intermediate. Furthermore, mutational analyses show that there is a strong correlation between the abili

SUBMITTER: Zhang X 

PROVIDER: S-EPMC2630804 | biostudies-literature | 2008 Sep

REPOSITORIES: biostudies-literature