In eukaryotes, protein translocation across the endoplasmic reticulum is mediated by a signal recognition particle, a small ribonucleoprotein (RNP) containing 7SL RNA. We have cloned and sequenced the gene coding for the Trypanosoma brucei 7SL RNA homologue and found that its sequence shows the highest degree of similarity to the human 7SL RNA sequence. In keeping with the prototype secondary structure of eukaryotic 7SL RNA, the trypanosome 7SL RNA secondary structure can be folded into four domains. The 7SL RNP, which sediments at approximately 11S on sucrose density gradients, was partially purified using column chromatography. A particle containing a 76-nucleotide-long RNA co-purified with the 7SL RNP; however, these particles did not co-fractionate by non-denaturing polyacrylamide gel electrophoresis.
Bibliographical noteFunding Information:
We wish to thank Christian Tschudi, Frank Richards, T. Guy Roberts and Kenneth P. Watkins for their interest and advice and Byron C. Hann and Peter Walter for providing the anti-54 kDa antibodies. This work was supported by grants from Catherine T. MacArthur Foundation and by Public Health Service grants AI-08614 to F.F. Richards and 5R01 AI-21975 to N.A. from the National Institutes of Health. N.A. is a Burroughs Wellcome Scholar of Molecular Parasitology.
- 7SL RNA
- Signal recognition particle