The cost of exposing a hydrophobic loop and implications for the functional role of 4.5 S RNA in the Escherichia coli signal recognition particle.
The signal recognition particle (SRP) is an RNA-protein complex that directs ribosomes to the rough endoplasmic reticulum membrane by binding to targeting signals found on the nascent chain of proteins destined for export to the endoplasmic reticulum. We found evidence from studies with fragments of the protein component of the Escherichia coli SRP that a long hydrophobic loop (the so-called "finger loop") is detrimental to the stability of its signal peptide-binding domain, the M domain. This hydrophobic loop is highly conserved and thus may have a critical role in the function of the SRP. Given our previously reported evidence that 4.5 S RNA stabilizes the tertiary fold of the M domain (Zheng, N., and Gierasch, L. M. (1997) Mol. Cell 1, 79-87), we now propose that the functional requirement for 4.5 S RNA resides in its ability to counteract the destabilizing influence of the finger loop.
Cleverley
R M
RM
Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachussets 01003, USA.
Zheng
N
N
Gierasch
L M
LM
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D018870:Endoplasmic Reticulum, Rough / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D006801:Humans; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D012329:RNA, Bacterial; D012335:RNA, Ribosomal / Q000737:chemistry*; D011994:Recombinant Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D018271:Signal Recognition Particle / Q000737:chemistry*; D013997:Time Factors
C409968:4.5S RNA; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; D012329:RNA, Bacterial; D012335:RNA, Ribosomal; D011994:Recombinant Proteins; D018271:Signal Recognition Particle; D012313:RNA