There are several instances of the identification of mtDNA-binding proteins that display a preference for single-stranded DNA .These are likely to be standard single-stranded DNA-binding proteins,because their sequences closely resemble Escherichia coli SSB ,which has facilitated their cloning. It will be of interest to learn the possible association of mitochondrial SSB with mtDNA polymerase in the replication complex and to determine whether mutations or deficiencies in mitochondrial SSB protein can cause mtDNA deletions in human disease. In the case of Drosophila, E. coli SSB is able
to stimulate the rate of DNA synthesis in vitro by mtDNA polymerase. The current working model for mammalian mtDNA replication is depicted in Figure 4 of the chapter by Brush and Kelly (this volume)