Escherichia coli SRP, its protein subunit Ffh, and the Ffh M domain are able to selectively limit membrane protein expression when overexpressed.
The Escherichia coli signal recognition particle (SRP) system plays an important role in membrane protein biogenesis. Previous studies have suggested indirectly that in addition to its role during the targeting of ribosomes translating membrane proteins to translocons, the SRP might also have a quality control role in preventing premature synthesis of membrane proteins in the cytoplasm. This proposal was studied here using cells simultaneously overexpressing various membrane proteins and either SRP, the SRP protein Ffh, its 4.5S RNA, or the Ffh M domain. The results show that SRP, Ffh, and the M domain are all able to selectively inhibit the expression of membrane proteins. We observed no apparent changes in the steady-state mRNA levels or membrane protein stability, suggesting that inhibition may occur at the level of translation, possibly through the interaction between Ffh and ribosome-hydrophobic nascent chain complexes. Since E. coli SRP does not have a eukaryote-like translation arrest domain, we discuss other possible mechanisms by which this SRP might regulate membrane protein translation when overexpressed.
Yosef
Ido
I
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel.
Bochkareva
Elena S
ES
Bibi
Eitan
E
D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018271:Signal Recognition Particle / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; D008565:Membrane Proteins; D021122:Protein Subunits; D018271:Signal Recognition Particle