Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations within or outside the cell. Proteins can be targeted to the inner space of an organelle, different intracellular membranes, the plasma membrane, or to the exterior of the cell via secretion. Information contained in the protein itself directs this delivery process. Correct sorting is crucial for the cell; errors or dysfunction in sorting have been linked to multiple diseases.
Ribosomes are macromolecular machines, found within all cells, that perform biological protein synthesis. Ribosomes link amino acids together in the order specified by the codons of messenger RNA molecules to form polypeptide chains. Ribosomes consist of two major components: the small and large ribosomal subunits. Each subunit consists of one or more ribosomal RNA molecules and many ribosomal proteins. The ribosomes and associated molecules are also known as the translational apparatus.
In biology, translation is the process in living cells in which proteins are produced using RNA molecules as templates. The generated protein is a sequence of amino acids. This sequence is determined by the sequence of nucleotides in the RNA. The nucleotides are considered three at a time. Each such triple results in addition of one specific amino acid to the protein being generated. The matching from nucleotide triple to amino acid is called the genetic code. The translation is performed by a large complex of functional RNA and proteins called ribosomes. The entire process is called gene expression.
A signal peptide is a short peptide present at the N-terminus of most newly synthesized proteins that are destined toward the secretory pathway. These proteins include those that reside either inside certain organelles, secreted from the cell, or inserted into most cellular membranes. Although most type I membrane-bound proteins have signal peptides, most type II and multi-spanning membrane-bound proteins are targeted to the secretory pathway by their first transmembrane domain, which biochemically resembles a signal sequence except that it is not cleaved. They are a kind of target peptide.
Cycloheximide is a naturally occurring fungicide produced by the bacterium Streptomyces griseus. Cycloheximide exerts its effects by interfering with the translocation step in protein synthesis, thus blocking eukaryotic translational elongation. Cycloheximide is widely used in biomedical research to inhibit protein synthesis in eukaryotic cells studied in vitro. It is inexpensive and works rapidly. Its effects are rapidly reversed by simply removing it from the culture medium.
Bacterial translation is the process by which messenger RNA is translated into proteins in bacteria.
Eukaryotic translation is the biological process by which messenger RNA is translated into proteins in eukaryotes. It consists of four phases: initiation, elongation, termination, and recapping.
N-Formylmethionine is a derivative of the amino acid methionine in which a formyl group has been added to the amino group. It is specifically used for initiation of protein synthesis from bacterial and organellar genes, and may be removed post-translationally.
Dipeptidyl peptidase-4, also known as adenosine deaminase complexing protein 2 or CD26 is a protein that, in humans, is encoded by the DPP4 gene. DPP4 is related to FAP, DPP8, and DPP9. The enzyme was discovered in 1966 by Hopsu-Havu and Glenner, and as a result of various studies on chemism, was called dipeptidyl peptidase IV [DP IV].
Protein metabolism denotes the various biochemical processes responsible for the synthesis of proteins and amino acids (anabolism), and the breakdown of proteins by catabolism.
mRNA display is a display technique used for in vitro protein, and/or peptide evolution to create molecules that can bind to a desired target. The process results in translated peptides or proteins that are associated with their mRNA progenitor via a puromycin linkage. The complex then binds to an immobilized target in a selection step. The mRNA-protein fusions that bind well are then reverse transcribed to cDNA and their sequence amplified via a polymerase chain reaction. The result is a nucleotide sequence that encodes a peptide with high affinity for the molecule of interest.
Eukaryotic translation termination factor1 (eRF1), also referred to as TB3-1 or SUP45L1, is a protein that is encoded by the ERF1 gene. In Eukaryotes, eRF1 is an essential protein involved in stop codon recognition in translation, termination of translation, and nonsense mediated mRNA decay via the SURF complex.
Elongation factor 4 (EF-4) is an elongation factor that is thought to back-translocate on the ribosome during the translation of RNA to proteins. It is found near-universally in bacteria and in eukaryotic endosymbiotic organelles including the mitochondria and the plastid. Responsible for proofreading during protein synthesis, EF-4 is a recent addition to the nomenclature of bacterial elongation factors.
Dipeptidyl-peptidase 3 is an enzyme that in humans is encoded by the DPP3 gene.
Eukaryotic translation initiation factor 2A (eIF2A) is a protein that in humans is encoded by the EIF2A gene. The eIF2A protein is not to be confused with eIF2α, a subunit of the heterotrimeric eIF2 complex. Instead, eIF2A functions by a separate mechanism in eukaryotic translation.
Puromycin-sensitive amino peptidase also known as cytosol alanyl aminopeptidase or alanine aminopeptidase (AAP) is an enzyme that in humans is encoded by the NPEPPS gene. It is used as a biomarker to detect damage to the kidneys, and that may be used to help diagnose certain kidney disorders. It is found at high levels in the urine when there are kidney problems.
A protein synthesis inhibitor is a compound that stops or slows the growth or proliferation of cells by disrupting the processes that lead directly to the generation of new proteins.
mRNA surveillance mechanisms are pathways utilized by organisms to ensure fidelity and quality of messenger RNA (mRNA) molecules. There are a number of surveillance mechanisms present within cells. These mechanisms function at various steps of the mRNA biogenesis pathway to detect and degrade transcripts that have not properly been processed.
Ribosomes are a large and complex molecular machine that catalyzes the synthesis of proteins, referred to as translation. The ribosome selects aminoacylated transfer RNAs (tRNAs) based on the sequence of a protein-encoding messenger RNA (mRNA) and covalently links the amino acids into a polypeptide chain. Ribosomes from all organisms share a highly conserved catalytic center. However, the ribosomes of eukaryotes are much larger than prokaryotic ribosomes and subject to more complex regulation and biogenesis pathways. Eukaryotic ribosomes are also known as 80S ribosomes, referring to their sedimentation coefficients in Svedberg units, because they sediment faster than the prokaryotic (70S) ribosomes. Eukaryotic ribosomes have two unequal subunits, designated small subunit (40S) and large subunit (60S) according to their sedimentation coefficients. Both subunits contain dozens of ribosomal proteins arranged on a scaffold composed of ribosomal RNA (rRNA). The small subunit monitors the complementarity between tRNA anticodon and mRNA, while the large subunit catalyzes peptide bond formation.
Modeccin is a toxic lectin, a group of glycoproteins capable of binding specifically to sugar moieties. Different toxic lectins are present in seeds of different origin. Modeccin is found in the roots of the African plant Adenia digitata. These roots are often mistaken for edible roots, which has led to some cases of intoxication. Sometimes the fruit is eaten, or a root extract is drunk as a manner of suicide.
