Too long for translocation?

sea-maid submitted, created time 7 months 4 weeks (www.jcb.org)

To explore SRP's role in vivo, the authors of this paper prepared a mutated version of human SRP14 that specifically lacked the delaying function.

SRP14's ability to bind to nascent peptides and to the SRP receptor remained intact. In cells that carried the mutant SRP, elongation sped up, but the final concentration of secreted protein dropped and growth suffered. Closer inspection revealed that translocation in these cells had slowed down and nascent peptide chains were being degraded.

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SRP Keeps Polypeptides Translocation-Competent

kavin submitted, created time 8 months 4 days (www.cell.com)

As we know, SRP is essential for targeting nascent chains to the endoplasmic reticulum, and it delays nascent chain elongation in cell-free translation systems. In this study, authors depleted mammalian cells of SRP14 by expressing mutant versions of the protein lacking the elongation arrest function. And they suggested that SRP can ensure that nascent chains remain translocation competent during the targeting time window dictated by SR. Since SRP-signal sequence affinities vary, the delay may also regulate which proteins are preferentially targeted.

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Interaction of signal-recognition particle 54 GTPase domain and signal-recognition particle RNA in the free signal-recognition particle

jackson submitted, created time 1 year 3 months (www.pnas.org)

The signal-recognition particle (SRP) is a ubiquitous protein–RNA complex that targets proteins to cellular membranes for insertion or secretion. A key player in SRP-mediated protein targeting is the evolutionarily conserved core consisting of the SRP RNA and the multidomain protein SRP54.

2 comments | Blog It | Email It | Keywords: signal-recognition particle SRP cellular membrane protein