This happens in the process of protein synthesis.
Protein synthesis occurs on ribosomes in the cytoplasm of a cell but is controlled by DNA located in the nucleus....
What is the role of messenger RNA and ribosomes in protein synthesis
The genome contains approximately 80 genes encoding cytochrome P450 proteins, among whose roles is the metabolism of “xenobiotics”. A number of P450 genes respond to compounds that induce mammalian cytochrome P450 genes (). Transcription of one gene in particular, CYP35A2, is strongly induced by exposure to ß-naphthoflavone and expression is exclusively in the intestine.
The maternally-provided transcription factor has been well studied for its role in specification of cell fate in the early embryo but has long been suspected of having an additional role in intestinal differentiation and/or intestinal function (; ). The proposed somatic function of is to regulate a bank of genes, possibly all intestinal, that are involved in “phase II” detoxification and that provide protection against reactive oxygen species and other environmental toxins (). One example of such a gene is , encoding the enzyme glutamylcysteine synthetase involved in the production of glutathione. A ::GFP reporter construct is expressed in the intestine, pharynx and ASI neurons; intestinal expression is induced by heat or by oxidative stress and is abolished either by mutating a binding site in the promoter or by abolishing activity (). Thermal or oxidative stress causes a ::GFP reporter protein to relocate from intestinal cytoplasm to intestinal nuclei within minutes (see ). The distribution of protein between nucleus and cytoplasm reflects competition between two kinases: glycogen synthase kinase-3 and p38 MAP kinase (; ). Consistent with a function of in regulating intestinal detoxification genes, mutants show shorter lifespans and are more sensitive to agents such as paraquat ().
All steps of protein synthesis easily ..
It is difficult to disagree with the lament that “unfortunately, the biology of digestion (in ) represents something of a blind spot in this otherwise remarkably well-characterised organism” (). However, digestion and metabolism have been studied in other nematodes (; ) and there is increasing understanding of these processes in as well. For example, analysis of a SAGE library prepared from dissected adult intestines identifies transcripts from over four thousand genes () and this list of genes must hold many keys to understanding digestion, metabolism and other aspects of intestinal physiology. In this section, we will highlight genes that are expressed highly, often exclusively, in the intestine and for which a functional role in digestion and metabolism is either known or plausible.
A number of further proteins show distinct apical localization within the intestine but may not play a primary role in enterocyte structure. Many of these proteins could be equally well discussed in later sections on digestion, metabolism, channels and transporters but are described here because what is presently known about their subcellular distribution appears more striking than what is known about their function:
15/01/2018 · Protein Synthesis Within the nuclei of ..
The intestine becomes active in endocytosis at least by the 8E cell stage, when there is transfer of yolk into the intestine primordium from the remainder of the embryo (; ). Once the animal hatches and begins to feed, nutrient uptake and trafficking must become an even larger fraction of intestinal activity, one that is just beginning to be investigated. Digestive and protective molecules must be secreted into the intestinal lumen and displayed on the apical plasma membranes. Nutrients must be taken up, either by endocytosis or by dedicated transporters. Processed food must be passed on to the rest of the animal through basolateral domains, either as building blocks or as synthesized products such as the vitellogenins. Similarly, there must be a variety of molecules, ranging from waste products to signals, passing in the opposite direction, back across the intestine basal surface from the rest of the animal. Thus one would expect that the intestine is a hotbed of endocytosis, exocytosis and trafficking in general. Consistent with such a view, the intestine cell cytoplasm is filled with rough endoplasmic reticulum but smooth ER is either rare or absent ().
is a schematic representation of a enterocyte, one of the pair of large, roughly centrosymmetric cells that surround the intestinal lumen and that constitute the basic unit of an “int” ring. The present section will emphasize the sub-cellular structures and molecular localizations within the enterocyte, leaving questions of function until later. The section is organized by cellular domain: (see ) the apical domain including brush border and terminal web; (see ) the basolateral domain including the basement membrane; (see ) the apical junctions joining one enterocyte to its partner and to adjacent ints within the overall intestinal structure, and; (see ) several of the intestine's organelles and inclusions. The spatial distribution of each protein discussed will be summarized on , including proteins for which a role in intestine structure can reasonably be surmised (e.g., actin in microvilli) as well as proteins that were investigated for other reasons (often because of a role in neurons) but whose major site of expression then turned out to be in the intestine.
Outline the role of ribosomes in protein synthesis
instead of being involved in protein synthesis.
The smooth ER plays an important role in carbohydrate metabolism, drug detoxification and lipid biosynthesis.
Mechanisms of Protein Synthesis by the Ribosome
- Site of protein synthesis.
Protein Synthesis - Department of Chemistry
Ribosomes on the outer surface of the endoplasmic reticulum play an important role in protein synthesis within cells.
Role of Ribosomes in Protein Synthesis | Genetics
PPI plays a big role in the cell-signalling cascade; for instance, dephosphorylation of glycogen synthase by protein phosphatase-1 results in glycogen synthesis.
When are ribosomes used in the process of protein synthesis
We thus propose the simple model (see ) that, following endoderm specification, participates in all acts of transcription in the intestine. However, other transcription factors are clearly present in the intestine (see below) and are likely to modulate the action of in different developmental or environmental circumstances. Transcription of the vitellogenin genes in the hermaphrodite intestine provides a possible example how this could occur. The vitellogenin (yolk protein) genes are expressed in the adult hermaphrodite intestine but not in the male intestine (). It had been known for some time that the gene is involved in repressing male vitellogenin synthesis () and Yi and Zarkower have shown that this effect is direct (). The protein shows similarity to , which, among other things, is also responsible for sex-specific regulation of yolk protein synthesis in flies (). The preferred binding sequence was identified and related sequences were then identified in the promoters of the half-dozen vitellogenin genes (). binds directly to one such site in an abbreviated promoter-reporter construct from the gene and mutation of this site causes reporter gene derepression in male intestines. A critical GATA site (; ) lies immediately adjacent to this site, suggesting that could act in the male intestine by repressing the activity of . GATA-like sites also lie in the vicinity of sites found in other vitellogenin gene promoters (; ; ).
Human Physiology - Cell structure and function - EKU
Organelles are specialized membrane-bound structures present inside a eukaryotic cell, and have specific and precise roles in various cellular processes.
Cell Components and Functions of Cell Organelles
The structural basis for TnaC-mediated translational stalling wasaddressed by obtaining a 5.8-Å cryo-EM map of the ribosome stalled byTnaC and high concentrations of tryptophan (Fig. 8). The cryo-EM datashows that the nascent chain adopts a distinct conformation in the exittunnel. We applied MDFF to obtain an atomic model of the entire ribosomeand the stalling nascent chain (Fig. 8F). The model allowed us to mapthe contacts between TnaC and the exit tunnel, as well as proposepossible communication pathways that would lead to inactivation of thecatalytic center of the ribosome (the so-called peptidyltransferasecenter, or PTC). One of the main findings was that two criticalribosomal residues at the PTC adopt conformations that are incompatiblewith cohabitation by release factors, which catalyze termination ofprotein synthesis.
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