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Up to 2% of mammalian proteome is post-translationally modified with isoprenoid lipids. Many of these molecules are key regulators of signaling pathways involved in cellular homeostasis. Appropriate signaling by prenylated proteins requires a combination of correct expression levels, efficient post-translational modification, correct subcellular trafficking and nanolocalisation as well as an appropriately...
Covalently linked to the C-terminus of many proteins, the glycosyl-phosphatidylinositol (GPI) anchor provides a means to anchor the attached protein to the cell membrane. Whilst the GPI anchor of mature proteins may be extensively modified, all GPI anchors possess a common core structure comprising of a phosphoethanolamine linker and a phosphatidylinositol lipid tail, separated by a glycan core. GPI-anchored...
Protein oxidation is a post-translational modification that can have beneficial or detrimental effects on cells. The interaction of reactive oxygen species (ROS) with proteins leads to their oxidation and ROS may be produced by several different enzymes. The first section of this review examines the major intracellular sources of ROS, with special attention paid to mitochondria and NADPH oxidases...
S-nitrosylation is a post-translational modification that is found to regulate increasing number of cellular and physiological functions such as neurotransmission, vesicle trafficking, gene expression and apoptosis in the biological system. This modification involves the attachment of nitric oxide (NO) covalently to the cysteine residue within the functional domains of proteins. However, imbalance...
Congenital Disorders of Glycosylation (CDG) form a group of inborn errors of metabolism, first described by Jaeken in 1987. Since then the molecular basis has been delineated in 23 different CDG subtypes. All underlying molecular defects in CDG interfere with the process of glycosylation, thus having functional consequences for many proteins. In the majority of the CDG subtypes the molecular defect...
Dystroglycan is a major cell surface receptor for extracellular matrix (ECM) proteins, including laminins, agrin, and perlecan, and glycosylation of dystroglycan by genes involved in the synthesis of its O-linked mannosyl glycans is necessary for ECM binding. Consistent with an essential role for these carbohydrate structures, loss of function mutations in genes affecting O-linked mannose biosynthesis...
The main target of cAMP action in the cell is cAMP-dependent protein kinase (PKA) which exists mainly as two different isozymes, designated as type I (PKA-I) and type II (PKA-II) (more isozymes may exist). The two isoforms are distinct in their physico-chemical properties; the unexpectedly great differences between two isoforms of the same kinase that are both under tight control by the cAMP molecule...
Protein kinase C stands for a family of phospholipid binding/dependent serine/threonine kinases consisting of ten members subdivided into three subgroups, classical PKCs (α, βI, βII, γ), novel PKCs (δ, ε, η, θ), and atypical PKCs (ζ, ι/λ), according to specific cofactor requirements. Tissue distribution and cellular compartmentalization imply differential, isoform-specific functions linked to distinct...
Maintaining a steady balance between energy production and consumption is a cornerstone of all living cells. Failure to maintain this balance affects most, if not all, cellular activities as these processes are normally tightly coupled to the energy status of the cell. It is beginning to emerge that human diseases such as obesity, Type 2 diabetes, and even certain types of cancer may be linked to...
Protein phosphorylation is a critical cellular process regulated by the competing actions of protein kinases (PKs) and phosphatases (PPs). While several hundred PKs exist in mammalian cells, there are only a few dozen PPs. PPs typically target Ser/Thr or Tyr residues but each has different characteristics and specificities and fall into three separate classes. PPs on their own have poor substrate...
The dynamic interchange of information within a cell, which subsumes the regulation of protein function, activity and multiprotein complex membership, depends upon the flux of the sets of modifications of proteins present in a specific cell at defined times, and the actions of various modules recruited to the resulting interaction platforms. These modifications interact functionally with each other...
The ubiquitination of a protein may promote proteasomal degradation, protein–protein interactions, lysosomal degradation or intracellular trafficking. Transcription factors are targets for ubiquitination by E3-ligase proteins, which results in the regulation in their function. The degradation of transcription factors enables the rapid regulation of gene expression by the ubiquitin–proteasome system...
SUMOs are Small Ubiquitin-like Modifiers that are covalently conjugated to extensive sets of target proteins in cells to regulate their activity. A properly functioning sumoylation system is essential for eukaryotic life. The system comprises a set of conjugating enzymes known as E1, E2 and E3s and a set of deconjugating enzymes known as SENPs. Three mammalian SUMO family members have been identified,...
Endoplasmic reticulum-associated protein degradation (ERAD) is a cellular process that targets short-lived resident proteins and aberrant secretory proteins to the proteasome for degradation. ERAD is essential for maintaining the homeostasis of the secretory pathway, as the retention of misfolded proteins in the ER can lead to several diseases. The budding yeast Saccharomyces cerevisiae has been used...
Chromatin, which was once considered merely a structural component required for DNA packaging, is now recognized as a dynamic template governed by intricate regulation. Histone post-translational modifications (PTMs) contribute to chromatin dynamics and regulate fundamental biological processes including transcription, mitotic chromatin condensation and DNA repair following damage. To date, histone...
All processes of DNA metabolism require a high degree of coordination with the processes that modify chromatin structure. Recent experimental efforts have established that post-translational modifications of histones and chromatin remodeling activities are required for DNA repair. Dynamic changes of chromatin are the means to control accessibility, coordinate binding of repair and signaling proteins...
The reproducible and accurate expression of genetic information and the integrity of the human genome, both temporally and topographically, rely heavily on the biochemical ability of nuclear proteins to physically interact with each other, as well as with DNA and RNA, at the molecular level. The strength and specificity of these interactions is primarily determined by the intracellular concentrations...
Post-translational proteolytic modification by limited proteolysis is not only a biological process that produces biologically active proteins (peptides), but because almost all intracellular biologically active proteins are synthesized as pre-pro forms, ordered limited proteolysis by specific proteases is an essential process. We will discuss on the proteolytic modification to make biological active...
Proteolytic enzymes constitute around 2% of the human genome and are involved in all stages of cell and organism development from fertilization through to cell death. In the human genome the major classes of peptidases are represented by cysteine-, serine- and metalloenzymes, which possess a wide spectrum of substrate specificity and physiological functions. The identification of many novel peptidases...
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