Identification of a mammalian mitochondrial homolog of ribosomal protein S7

Bovine mitochondrial small subunit ribosomal proteins were separated by two -dimensional electrophoresis, The region containing the most basic protein( s) was excised and the protein(s) present subjected to in-gel digestion wit h trypsin, Electrospray tandem mass spectrometry was used to provide sequen ce information on some of the peptide products. Searches of the human EST d atabase using the sequence of the longest peptide analyzed indicated that t his peptide was from the mammalian mitochondrial homolog of prokaryotic rib osomal protein S7 (MRP S7(human)). MRP S7(human) is a 28-kDa protein with a pi of 10. Significant homology to bacterial S7 is observed especially in t he C-terminal half of the protein. Surprisingly, MRP S7(human) shows less h omology to the corresponding mitochondrial proteins from plants and fungi t han to bacterial S7, (C) 1999 Academic Press.