当前位置： SCI文献检索 > JOURNAL OF MOLECULAR BIOLOGY期刊下所有文献 > The code for directing proteins for translocation across ER membrane: SRP cotranslationally recognizes specific features of a signal sequence.

The code for directing proteins for translocation across ER membrane: SRP cotranslationally recognizes specific features of a signal sequence.

Abstract：

:The signal recognition particle (SRP) cotranslationally recognizes signal sequences of secretory proteins and targets ribosome-nascent chain complexes to the SRP receptor in the endoplasmic reticulum membrane, initiating translocation of the nascent chain through the Sec61 translocon. Although signal sequences do not have homology, they have similar structural regions: a positively charged N-terminus, a hydrophobic core and a more polar C-terminal region that contains the cleavage site for the signal peptidase. Here, we have used site-specific photocrosslinking to study SRP-signal sequence interactions. A photoreactive probe was incorporated into the middle of wild-type or mutated signal sequences of the secretory protein preprolactin by in vitro translation of mRNAs containing an amber-stop codon in the signal peptide in the presence of the N(ε)-(5-azido-2 nitrobenzoyl)-Lys-tRNA(amb) amber suppressor. A homogeneous population of SRP-ribosome-nascent chain complexes was obtained by the use of truncated mRNAs in translations performed in the presence of purified canine SRP. Quantitative analysis of the photoadducts revealed that charged residues at the N-terminus of the signal sequence or in the early part of the mature protein have only a mild effect on the SRP-signal sequence association. However, deletions of amino acid residues in the hydrophobic portion of the signal sequence severely affect SRP binding. The photocrosslinking data correlate with targeting efficiency and translocation across the membrane. Thus, the hydrophobic core of the signal sequence is primarily responsible for its recognition and binding by SRP, while positive charges fine-tune the SRP-signal sequence affinity and targeting to the translocon.

journal_name

J Mol Biol

journal_title

Journal of molecular biology

authors

Nilsson I,Lara P,Hessa T,Johnson AE,von Heijne G,Karamyshev AL

doi

10.1016/j.jmb.2014.06.014

subject

Has Abstract

pub_date

2015-03-27 00:00:00

pages

1191-201

issue

6 Pt A

eissn

0022-2836

issn

1089-8638

pii

S0022-2836(14)00307-6

journal_volume

427

pub_type

杂志文章

在线工具

The code for directing proteins for translocation across ER membrane: SRP cotranslationally recognizes specific features of a signal sequence.