Four Related Proteins of the Trypanosoma brucei RNA Editing Complex

Abstract

RNA editing in kinetoplastid mitochondria occurs by a series of enzymatic steps that is catalyzed by a macromolecular complex. Four novel proteins and their corresponding genes were identified by mass spectrometric analysis of purified editing complexes fromTrypanosoma brucei. These four proteins, TbMP81, TbMP63, TbMP42, and TbMP18, contain conserved sequences to various degrees. All four proteins have sequence similarity in the C terminus; TbMP18 has considerable sequence similarity to the C-terminal region of TbMP42, and TbMP81, TbMP63, and TbMP42 contain zinc finger motif(s). Monoclonal antibodies that are specific for TbMP63 and TbMP42 immunoprecipitate in vitro RNA editing activities. The proteins are present in the immunoprecipitates and sediment at 20S along with the in vitro editing, and RNA editing ligases TbMP52 and TbMP48. Recombinant TbMP63 and TbMP52 coimmunoprecipitate. These results indicate that these four proteins are components of the RNA editing complex and that TbMP63 and TbMP52 can interact.

ACKNOWLEDGMENTS

We thank Barbara Morach, Brian Panicucci, Jeff O'Rear, Micaiah Evans, and RoseMary Reed for technical help, Maciek Drozdz for communicating unpublished results, Peter Myler for helpful suggestions, Elizabeth Wayner for assistance in MAb production, Sandy Kielland for N-terminal microsequencing, John Donelson for clone T651, and Najib El Sayed for providing several genomic clones. Sequence data were obtained from The Institute for Genomic Research (http://www.tigr.org) and The Sanger Centre (http://www.sanger.ac.uk) websites that were supported by NIAID and The Wellcome Trust as part of the Trypanosoma Genome Network that was coordinated with support from the TDR section of the World Health Organization.

This work was supported by NIH Postdoctoral Fellowship AI10312 to R.I., NIH grant HG00041 to S.G., grants IR33 CA84698 and RO1 A141109-01 to R.A., NIH grants AI14102 and GM4218 to K.S., and HFSPO grant RG0316/1997 M.