Identification of mammalian mitochondrial ribosomal proteins (MRPs) by N-terminal sequencing of purified bovine MRPs and comparison to data bank sequences: The large subribosomal particle

Bovine mitochondrial ribosomes are presented as a model system for mammalia n mitochondrial ribosomes. An alternative system for identifying individual bovine mitochondrial ribosomal proteins (MRPs) by RP-HPLC is described. To identify and to characterize individual MRPs proteins were purified from b ovine liver, separated by RP-HPLC, and identified by 2D PAGE techniques and immunoblotting. Molecular masses of individual MRPs were determined. Selec ted proteins were subjected to N-terminal amino acid sequencing. The peptid e sequences obtained were used to screen different databases to identify se veral corresponding MRP sequences from human, mouse, rat, and yeast. Signal sequences for mitochondrial import were postulated by comparison of the bo vine mature N-termini determined by amino acid sequencing with the deduced mammalian MRP sequences. Significant sequence similarities of these new MRP s to known r-proteins from other sources, e.g., E. coli, were detected only for two of the four MRP families presented. This finding suggests that mam malian mitochondrial ribosomes contain several novel proteins. Amino acid s equence information for all of the bovine MRPs will prove invaluable for as signing functions to their genes, which would otherwise remain unknown.