Characterization of the RNA degradosome of Pseudoalteromonas haloplanktis: conservation of the RNase E-RhlB interaction in the gammaproteobacteria.
The degradosome is a multienzyme complex involved in mRNA degradation in Escherichia coli. The essential endoribonuclease RNase E contains a large noncatalytic region necessary for protein-protein interactions with other components of the RNA degradosome. Interacting proteins include the DEAD-box RNA helicase RhlB, the glycolytic enzyme enolase, and the exoribonuclease PNPase. Pseudoalteromonas haloplanktis, a psychrotolerant gammaproteobacterium distantly related to E. coli, encodes homologs of each component of the RNA degradosome. In P. haloplanktis, RNase E associates with RhlB and PNPase but not enolase. Plasmids expressing P. haloplanktis RNase E (Ph-RNase E) can complement E. coli strains lacking E. coli RNase E (Ec-RNase E). Ph-RNase E, however, does not confer a growth advantage to E. coli at low temperature. Ph-RNase E has a heterologous protein-protein interaction with Ec-RhlB but not with Ec-enolase or Ec-PNPase. The Ph-RNase E binding sites for RhlB and PNPase were mapped by deletion analysis. The PNPase binding site is located at the C-terminal end of Ph-RNase E at the same position as that in Ec-RNase E, but the sequence of the site is not conserved. The sequence of the RhlB binding site in Ph-RNase E is related to the sequence in Ec-RNase E. Together with the heterologous interaction between Ph-RNase E and Ec-RhlB, our results suggest that the underlying structural motif for the RNase E-RhlB interaction is conserved. Since the activity of Ec-RhlB requires its physical interaction with Ec-RNase E, conservation of the underlying structural motif over a large evolutionary distance could be due to constraints involved in the control of RhlB activity.
Aït-Bara
Soraya
S
Laboratoire de Microbiologie et Génétique Moléculaires, UMR 5100, Centre National de la Recherche Scientifique et Université de Toulouse 3, 31062 Toulouse, France.
Carpousis
Agamemnon J
AJ
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli; D020563:Gammaproteobacteria / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D020871:RNA Stability / Q000235:genetics* / Q000502:physiology; D012329:RNA, Bacterial / Q000378:metabolism*
D001426:Bacterial Proteins; D012329:RNA, Bacterial; D004722:Endoribonucleases; C022537:ribonuclease E