An Escherichia coli gene showing a potential ancestral relationship to the genes for the mitochondrial import site proteins ISP42 and MOM38

Abstract

An ORF (OrfT) of 1911 base pairs, upstream of the hip operon in Escherichia coli at map position 33.82 has been identified. The protein encoded by this sequence is predicted to have a molecular mass of 68,249 Da and the carboxyterminal 276 residues shows 26.8% and 25.4% identity with the import site proteins ISP42 and MOM38 from the mitochondrial outer membrane of Saccharomyces cerevisiae and Neurospora crassa, respectively. These mitochondrial membrane proteins have been shown to be essential components of the protein translocation apparatus in yeast. These similarities raise the possibility that OrfT might represent the bacterial gene from which these eukaryotic genes evolved.