Signal recognition particle causes a transient arrest in the biosynthesis of prepromelittin and mediates its translocation across XXXX endoplasmic reticulum.

@entity1 @entity1522 @entity3505
The translocation of prepromelittin (pPM) across @entity1 endoplasmic reticulum was studied in both @entity3505 germ and reticulocyte lysate. In the @entity3505 germ system, signal recognition particle (SRP) caused a transient arrest in the synthesis of pPM. This was indicated by a slowdown in the rate of synthesis of pPM in the presence of SRP. The arrest was specific, dependent on the concentration of SRP, and more effective at early incubation time. In a tightly synchronized translation system, SRP had no apparent effect on the elongation of pPM, indicating that the effect of SRP on pPM chain synthesis might be at the final stages of chain elongation and release from the ribosome. This was reflected in a transient accumulation of pPM as peptidyl tRNA. Because pPM is composed of only 70 @entity1522 , arrest by SRP may be very close to chain termination. Arrest at this stage of chain synthesis seems to be unstable and the nascent chain gets terminated and released from the ribosome after a transient delay. The translocation of pPM was shown to be dependent on both SRP and docking protein. The difference in the translocation efficiency of pPM in reticulocyte and @entity3505 germ lysates may reflect a difference in the targeting process in the two systems.
