The heterodimeric subunit SRP9/14 of the signal recognition particle functions as permuted single polypeptide chain.
AUTOR(ES)
Bovia, F
RESUMO
The targeting of nascent polypeptide chains to the endoplasmic reticulum is mediated by a cytoplasmic ribonucleoprotein, the signal recognition particle (SRP). The 9 kD (SRP9) and the 14 kD (SRP14) subunits of SRP are required to confer elongation arrest activity to the particle. SRP9 and SRP14 form a heterodimer which specifically binds to SRP RNA. We have constructed cDNAs that encode single polypeptide chains comprising SRP9 and SRP14 sequences in the two possible permutations linked by a 17 amino acid peptide. We found that both fusion proteins specifically bound to SRP RNA as monomeric molecules folded into a heterodimer-like structure. Our results corroborate the previous hypothesis that the authentic heterodimer binds to SRP RNA in equimolar ratio. In addition, both fusion proteins conferred elongation arrest activity to SRP(-9/14), which lacks this function, and one fusion protein could functionally replace the heterodimer in the translocation assay. Thus, the normal N-and C-termini of both proteins have no essential role in folding, RNA-binding and in mediating the biological activities. The possibility to express the heterodimeric complex as a single polypeptide chain facilitates the analysis of its functions and its structure in vivo and in vitro.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=308117Documentos Relacionados
- The SRP9/14 subunit of the human signal recognition particle binds to a variety of Alu-like RNAs and with higher affinity than its mouse homolog.
- The SRP9/14 subunit of the signal recognition particle (SRP) is present in more than 20-fold excess over SRP in primate cells and exists primarily free but also in complex with small cytoplasmic Alu RNAs.
- Binding sites of the 9- and 14-kilodalton heterodimeric protein subunit of the signal recognition particle (SRP) are contained exclusively in the Alu domain of SRP RNA and contain a sequence motif that is conserved in evolution.
- The signal recognition particle (SRP) database
- The decline in human Alu retroposition was accompanied by an asymmetric decrease in SRP9/14 binding to dimeric Alu RNA and increased expression of small cytoplasmic Alu RNA.