Mitochondrial DNA structure and function

Abstract

This chapter discusses mitochondrial DNA (mtDNA) structures and its functions. The human mtDNA is representative of mammalian mitochondrial genomes. Comparison of the nucleotide sequences of mammal mtDNA revealed some degree of conservation in the promoter regions as well as in three other regions (termed “Conserved Sequence Blocks,” or CSB I, CSB II, and CSB III). The mammalian mitochondrial genome has two modes of replication. The first one involves the asymmetric replication of the leading and lagging strands. The second one, based on the observation of replication intermediates in two-dimensional (2D) gels suggested that replication, in a certain number of mtDNA molecules, involves coupled leading- and lagging-strand synthesis. Many factors involved in mammalian mtDNA replication have been characterized. Because of its probable prokaryote origin, in many aspects, the mitochondrion behaves as an independent entity living inside an eukaryotic cell. All basic processes associated with life (DNA maintenance, transcription, and translation) occur inside the organelle. However, the vast majority of the factors involved in promoting and controlling these processes are borrowed from the cytoplasm, where nuclear-coded proteins are synthesized.