Mitochondrial protein structure

Not all the cellular DNA is in the nucleus some is found in the mitochondria. In addition, mitochondria contain RNA as well as several enzymes used for protein synthesis. Interestingly, mitochond-rial RNA and DNA bear a closer resemblance to the nucleic acid of bacterial cells than they do to animal cells. For example, the rather small DNA molecule of the mitochondrion is circular and does not form nucleosomes. Its information is contained in approximately 16,500 nucleotides that func-tion in the synthesis of two ribosomal and 22 transfer RNAs (tRNAs). In addition, mitochondrial DNA codes for the synthesis of 13 proteins, all components of the respiratory chain and the oxidative phosphorylation system. Still, mitochondrial DNA does not contain sufficient information for the synthesis of all mitochondrial proteins most are coded by nuclear genes. Most mitochondrial proteins are synthesized in the cytosol from nuclear-derived messenger RNAs (mRNAs) and then transported into the mito-chondria, where they contribute to both the structural and the functional elements of this organelle. Because mitochondria are inherited cytoplasmically, an individual does not necessarily receive mitochondrial nucleic acid equally from each parent. In fact, mito-chondria are inherited maternally. 

Abe Y et al. (2000) Structural basis of presequence recognition by the mitochondrial protein import receptor Tom20. Cell 100 551-560 Abrahamsen MS et al. (2004) Complete genome sequence of the apicomplexan, Cryptosporidium parvum. Science 304 441-445... 

Machius, M. Chuang, J.L. Wynn, R.M. Tomchick, D.R. Chuang, D.T. Structure of rat BCKD kinase nucleotide-induced domain communication in a mitochondrial protein kinase. Proc. Natl. Acad. Sci. USA, 98, 11218-11223 (2001)... 

The heme cofactors of a and b cytochromes are tightly, but not covalently, bound to their associated proteins the hemes of c-type cytochromes are covalently attached through Cys residues (Fig. 19-3). As with the flavoproteins, the standard reduction potential of the heme iron atom of a cytochrome depends on its interaction with protein side chains and is therefore different for each cytochrome. The cytochromes of type a and b and some of type c are integral proteins of the inner mitochondrial membrane. One striking exception is the cytochrome c of mitochondria, a soluble protein that associates through electrostatic interactions with the outer surface of the inner membrane. We encountered cytochrome c in earlier discussions of protein structure (see Fig. 4-18). 

Lister R, Whelan J (2006) Mitochondrial protein import convergent solutions for receptor structure. Curr Biol 16 R197-R199... 

ATP formation is coupled to the energetically downhill H+ movement back into the mitochondrial matrix through a hydrophobic protein factor in the inner membrane (F0 see footnote 5) and a protein factor (Fx) about 9 nm in diameter that protrudes from the inner membrane into the matrix (Fig. 6-9). Indeed, subunits of Fx rotate during ATP formation, so this protein structure has been called a rotary motor and has become a model for... 

Gencic, S., Schagger, H., and von Jagow, G., t99t. Core t protein of bovine ubiquinol-cytochrome-c reductase an additional member of the mitochondrial-protein-processing family. Cloning of bovine core I and core tt cDNAs and primary structure of the proteins, Eur. J. Biochem. 199 123nl31. 

Fig. 12.1. Relative sizes of mitochondrial and chloroplast chromosomes and location of protein structural genes. The figure was constructed from published data [5,15,17,22,26-28]. The structural genes are marked by wide sections. Black areas code for proteins. White areas are introns. 0x1, OxII and OxIII are subunits I, II and III of cytochrome c oxidase. Cyt b, cytochrome b. Fo and Fo, are subunits 6 and 9 of the proton ATPase complex. In the chloroplast chromosome the arrows indicate the transcription direction and the size of the transcripts. CF,a, CFj/8, CFjc and CFoIII are subunits a, /S, t and III of the chloroplast proton ATPase complex [30]. PSII5], PSII44, and PSII34 are subunits of photosystem II reaction center with the corresponding molecular weights of 51000, 44000 and 34000. PSI70 is subunit I of photosystem I reaction center. Cyt /is cytochrome/ cyt is cytochrome b and b -flV is subunit IV of cytochrome b(,-f complex.

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