Protein biosynthesis is a core biological process, occurring inside cells, balancing the loss of cellular proteins through the production of new proteins. Proteins perform a number of critical functions as enzymes, structural proteins or hormones. Protein synthesis is a very similar process for both prokaryotes and eukaryotes but there are some distinct differences.
A protein kinase is a kinase which selectively modifies other proteins by covalently adding phosphates to them (phosphorylation) as opposed to kinases which modify lipids, carbohydrates, or other molecules. Phosphorylation usually results in a functional change of the target protein (substrate) by changing enzyme activity, cellular location, or association with other proteins. The human genome contains about 500 protein kinase genes and they constitute about 2% of all human genes. There are two main types of protein kinase. The great majority are serine/threonine kinases, which phosphorylate the hydroxyl groups of serines and threonines in their targets. Most of the others are tyrosine kinases, although additional types exist. Protein kinases are also found in bacteria and plants. Up to 30% of all human proteins may be modified by kinase activity, and kinases are known to regulate the majority of cellular pathways, especially those involved in signal transduction.
In biochemistry, a kinase is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule donates a phosphate group to the substrate molecule. As a result, kinase produces a phosphorylated substrate and ADP. Conversely, it is referred to as dephosphorylation when the phosphorylated substrate donates a phosphate group and ADP gains a phosphate group. These two processes, phosphorylation and dephosphorylation, occur four times during glycolysis.
A mitogen-activated protein kinase is a type of protein kinase that is specific to the amino acids serine and threonine. MAPKs are involved in directing cellular responses to a diverse array of stimuli, such as mitogens, osmotic stress, heat shock and proinflammatory cytokines. They regulate cell functions including proliferation, gene expression, differentiation, mitosis, cell survival, and apoptosis.
Mitogen Activated Protein (MAP) kinase kinase kinase is a serine/threonine-specific protein kinase which acts upon MAP kinase kinase. Subsequently, MAP kinase kinase activates MAP kinase. Several types of MAPKKK can exist but are mainly characterized by the MAP kinases they activate. MAPKKKs are stimulated by a large range of stimuli, primarily environmental and intracellular stressors. MAPKKK is responsible for various cell functions such as cell proliferation, cell differentiation, and apoptosis. The duration and intensity of signals determine which pathway ensues. Additionally, the use of protein scaffolds helps to place the MAPKKK in close proximity with its substrate to allow for a reaction. Lastly, because MAPKKK is involved in a series of several pathways, it has been used as a therapeutic target for cancer, amyloidosis, and neurodegenerative diseases. In humans, there are at least 19 genes which encode MAP kinase kinase kinases:
Ribosome biogenesis is the process of making ribosomes. In prokaryotes, this process takes place in the cytoplasm with the transcription of many ribosome gene operons. In eukaryotes, it takes place both in the cytoplasm and in the nucleolus. It involves the coordinated function of over 200 proteins in the synthesis and processing of the three prokaryotic or four eukaryotic rRNAs, as well as assembly of those rRNAs with the ribosomal proteins. Most of the ribosomal proteins fall into various energy-consuming enzyme families including ATP-dependent RNA helicases, AAA-ATPases, GTPases, and kinases. About 60% of a cell's energy is spent on ribosome production and maintenance.
In molecular biology, ribosomal s6 kinase (rsk) is a family of protein kinases involved in signal transduction. There are two subfamilies of rsk, p90rsk, also known as MAPK-activated protein kinase-1 (MAPKAP-K1), and p70rsk, also known as S6-H1 Kinase or simply S6 Kinase. There are three variants of p90rsk in humans, rsk 1-3. Rsks are serine/threonine kinases and are activated by the MAPK/ERK pathway. There are two known mammalian homologues of S6 Kinase: S6K1 and S6K2.
Mitogen-activated protein kinase 14, also called p38-α, is an enzyme that in humans is encoded by the MAPK14 gene.
Dual specificity mitogen-activated protein kinase kinase 3 is an enzyme that in humans is encoded by the MAP2K3 gene.
Ribosomal protein S6 kinase alpha-1 is an enzyme that in humans is encoded by the RPS6KA1 gene.
protein S6 kinase, 90kDa, polypeptide 3, also s RPS6KA3, is an enzyme that in humans is encoded by the RPS6KA3 gene.
5'-AMP-activated protein kinase catalytic subunit alpha-1 is an enzyme that in humans is encoded by the PRKAA1 gene.
PAK3 is one of three members of Group I PAK family of evolutionary conserved serine/threonine kinases. PAK3 is preferentially expressed in neuronal cells and involved in synapse formation and plasticity and mental retardation.
Ribosomal protein S6 kinase alpha-4 is an enzyme that in humans is encoded by the RPS6KA4 gene.
Fas-activated serine/threonine kinase is an enzyme that in humans is encoded by the FASTK gene.
MAP kinase-activated protein kinase 5 is an enzyme that in humans is encoded by the MAPKAPK5 gene. The protein encoded by this gene is a member of the serine/threonine kinase family. In response to cellular stress and proinflammatory cytokines, this kinase is activated through its phosphorylation by MAP kinases, including MAPK1/ERK, MAPK14/p38-alpha, and MAPK11/p38-beta. In vitro, this kinase phosphorylates heat shock protein HSP27 at its physiologically relevant sites. Two alternately-spliced transcript variants of this gene encoding distinct isoforms have been reported.
40S ribosomal protein S18 is a protein that in humans is encoded by the RPS18 gene.
60S ribosomal protein L41 is a protein that is specific to humans and is encoded by the RPL41 gene, also known as HG12 and large eukaryotic ribosomal subunit protein eL41. The gene family HGNC is L ribosomal proteins. The protein itself is also described as P62945-RL41_HUMAN on the GeneCards database. This RPL41 gene is located on chromosome 12.
Eukaryotic Initiation Factor 2 (eIF2) is an eukaryotic initiation factor. It is required for most forms of eukaryotic translation initiation. eIF2 mediates the binding of tRNAiMet to the ribosome in a GTP-dependent manner. eIF2 is a heterotrimer consisting of an alpha, a beta, and a gamma subunit.
GCN2 is a serine/threonine-protein kinase that senses amino acid deficiency through binding to uncharged transfer RNA (tRNA). It plays a key role in modulating amino acid metabolism as a response to nutrient deprivation.
