In mitochondria which portion contains specific proteins

Mitochondria Mitochondria generate the energy that is needed to power the functions of the cell, but also participate directly in several other cellular processes, including apoptosis, cell cycle control and calcium homeostasis. Mitochondria are distributed throughout the cytoplasm and vary in number between different cell types. Each organelle is enclosed by a double membrane, with the inner one forming the characteristic folds known as cristae. Mutations causing mitochondrial dysfunction are often related to severe diseases. Examples of proteins localized to mitochondria can be seen in Figure 1. In the subcellular section, Figure 1. Examples of proteins localized to the mitochondria. The structure of mitochondria The mitochondrion was first described in 1890 by Richard Altmann. It is approximately 0.5-1 μm long and is enclosed by an outer and inner membrane seprated by an intermembrane space. The folds of the inner membrane, denoted cristae, enclose the aqueous matrix, which contains the mitochondrial DNA (mtDNA) and the majority of the mitochondrial proteins ( Table 1. Selection of proteins suitable as markers for mitochondria. Gene Description Substructure CS Citrate synthase Mitochondria LRPPRC Leucine rich pentatricopeptide repeat containing Mitochondria SLC25A24 Solute carrier family 25 member 24 Mitochondria TIMM44 Translocase of inner mitochondrial membrane 44 Mitochondria GCDH Glutaryl-CoA dehydrogenase Mitochondria TRAP1 TNF receptor associated protein 1 Mitoch...

\( \newcommand\) • • • • In eukaryotic cells, where reactions and proteins are often sequestered into specialized membrane-bound compartments (organelles), a system needs to be in place for the targeted movement of specific proteins from where they are made in the cell to where they are used in the cell. In this section we will discuss two major modes of protein localization. We will begin with the components of the endomembrane system. This system involves co-translational translocation across membranes, and later delivery and processing through various organelles via vesicles and motor protein-mediated transport. It is employed for proteins that function within the compartments of the endomembrane system, for proteins embedded in the plasma membrane, and for secreted proteins. We will also discuss another mode of protein targeting and translocation. This broad class of protein-targeting mechanisms occurs strictly post-translationally, and directs proteins to the nucleus, the mitochondria, the plastid, and the peroxisomes. It shares certain concepts- such as signal peptides- with the endomembrane system targeting mentioned above. Discussion: You have learned about many types of proteins so far in this class. Name a few of these proteins and their location within the cell. For example, where would you expect to find glycolytic enzymes? Design challenge Eukaryotic cells contain membrane-bound organelles that effectively separate materials, processes, and reactions from one ...

Most mitochondrial proteins are encoded in the nucleus. They are synthesized as precursor forms in the cytosol and must be imported into mitochondria with the help of different protein translocases. Distinct import signals within precursors direct each protein to the mitochondrial surface and subsequently onto specific transport routes to its final destination within these organelles. In this review we highlight common principles of mitochondrial protein import and address different mechanisms of protein integration into mitochondrial membranes. Over the last years it has become clear that mitochondrial protein translocases are not independently operating units, but in fact closely cooperate with each other. We discuss recent studies that indicate how the pathways for mitochondrial protein biogenesis are embedded into a functional network of various other physiological processes, such as energy metabolism, signal transduction, and maintenance of mitochondrial morphology. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids. Highlights ► Multiple import machineries mediate the sorting and assembly of nuclear encoded mitochondrial precursor proteins. ► Mitochondrial protein translocases operate as highly dynamic molecular machines. ► Close cooperation between translocation machineries of inner and outer membrane is crucial for mitochondrial protein sorting. ► Mitochondrial protein import is embedded into large-scal...

Mitochondria contain about 1,000–1,500 proteins that fulfil multiple functions. Mitochondrial proteins originate from two genomes: mitochondrial and nuclear. Hence, proper mitochondrial function requires synchronization of gene expression in the nucleus and in mitochondria and necessitates efficient import of mitochondrial proteins into the organelle from the cytosol. Furthermore, the mitochondrial proteome displays high plasticity to allow the adaptation of mitochondrial function to cellular requirements. Maintenance of this complex and adaptable mitochondrial proteome is challenging, but is of crucial importance to cell function. Defects in mitochondrial proteostasis lead to proteotoxic insults and eventually cell death. Different quality control systems monitor the mitochondrial proteome. The cytosolic ubiquitin–proteasome system controls protein transport across the mitochondrial outer membrane and removes damaged or mislocalized proteins. Concomitantly, a number of mitochondrial chaperones and proteases govern protein folding and degrade damaged proteins inside mitochondria. The quality control factors also regulate processing and turnover of native proteins to control protein import, mitochondrial metabolism, signalling cascades, mitochondrial dynamics and lipid biogenesis, further ensuring proper function of mitochondria. Thus, mitochondrial protein quality control mechanisms are of pivotal importance to integrate mitochondria into the cellular environment. Open Acc...