Protein Synthesis Protein Synthesis is the process whereby DNA (deoxyribonucleic acid) codes for the production of essential proteins, such as enzymes and hormones. Proteins are long chains of molecules called amino acids. Different proteins are made by using different sequences and varying numbers of amino acids. The smallest protein consists of fifty amino acids and the largest is about three thousand amino acids long. Protein synthesis occurs on ribosomes in the cytoplasm of a cell but is controlled by DNA located in the nucleus.
The nuclear envelope is attached to a network of membrane-enclosed tubules that extends throughout the cell called the endoplasmic reticulum. The nuclear envelope is perforated by many holes, called nuclear pores, that permit the movement of selected molecules between the nucleus and the rest of the cell, while blocking the passage of other molecules. The nucleus contains the nucleolus, which manufactures the organelle known as the ribosome, or the protein producing organism. Genetic information in the form of deoxyribonucleic acid(DNA) is stored in threadlike, tangled structures called chromatin within the nucleus. During the process of cell division known as mitosis, in which the nucleus divides, the chromatin condense into several distinct structures called chromosomes.
The diversity of antibodies is due to DNA rearrangement of germ-line DNA to produce vast number of genes encoding for antibodies (Karp, 2013). The antibodies consist of light (L) chains (kappa and lambda) and heavy (H) chains which are linked by disulfide bonds as shown in Figure 1 (Karp, 2013). Both of the heavy and light chains consist of variable (V) and constant (C) region. The immunoglobulin (Ig) genes are responsible in the production of membrane-bound and secreted antibodies (Reece et al., 2011). The production of light chain involves gene segments such as 40 variable (V) segments, 5 joining (J) segments, and a constant (C) segment.
Histones are alkaline proteins which play an important role in the packaging of DNA and the regulation of genes in eukaryotic organisms. Without histones, the unwound DNA in chromosomes would be very long, about 2 meters in length per cell. As a result, chromatin in the DNA is very tightly associated with these histone proteins, which package and order the DNA into structural units called nucleosomes. This supercoiled, condensed structure allows for the long DNA molecule to fit inside the nucleus. Selective winding and unwinding allows for portions of the DNA to be exposed.
They are presented on many secreted and membrane-bound glycoproteins. Figure 1.1 Representative high-mannose, complex, and hybrid type N-glycans. In Saccharomyces cerevisiae and vertebrates, they are initially synthesized on the cytoplasmic side of the endoplasmic reticulum (ER) membrane, starting with the transfer of N-acetylglucosamine phosphate (GlcNAc-P) from nucleotide-activated sugar donor UDP-GlcNAc to the ER membrane-anchored molecule dolichol phosphate (Dol-P). The dolichol pyrophosphate N-acetylglucosamine (Dol-P-P-GlcNAc) formed is further processed by glycosyltransferases. One GlcNAc and five mannose residues are subsequently added from UDP-GlcNAc and GDP-Man, respectively, generating Man5GlcNAc2-P-P-Dol.
In the nucleus MAP kinase phosphorylates other proteins and triggers many transcription factors including epidermal growth and platelet derived factors, interleukin, insulin, ect. The products produced by the MAP kinase cascade reach the nucleus to initiate the transcription of the relevant gene by the transduction of an extracellular signal as it propagates intracellular until it reaches the nucleus. Once the product has reached the nucleus, it nurtures and grows and becomes interpreted showing differentiation. Free ribosomes become associated with the endoplasmic reticulum to allow for the release of the synthesized protein into the rough endoplasmic reticulum by being unattached to any membrane.
2) Similarities and differences of the family of Ubiquitin; Structure The ubiquitin family is large, but shares a few characteristics. Some of these characteristics includes; the ubiquitin folding and the biochemical mechanism they use to bind to the target protein. The ubiquitin structure was analyzed as part of a larger NMR study to understand new techniques including H/D exchange. This technique contributed mostly on the information of the protein folding.
It is separated from the rest of the cell by a double membrane (envelop), which has pores to allow the movement of substances in or out. For example, messenger RNA passes out of the nucleus during protein synthesis. (Clamp, 2000, pg. 102) Endoplasmic reticulum is a system of membranes found in the cytoplasm of a cell. The ER provides a very large surface area for chemical reactions within the cell.
This protective role may account for its increased levels within cells. In eukaryotic cells, pre-mRNA undergoes extensive post-transcriptional modifications to become mature mRNA. The modifications to pre-mRNA include 5’ end capping, 3’ end cleavage and polyadenylation, and the splicing of introns (Gu and Lima, 2005). The spliceosome is a large RNA-protein complex, which removes introns from pre-mRNA. Key components of the spliceosome are small nuclear ribonucleproteins (snRNPs).
Previous study has shown that SR proteins undergo multiple rounds of phosphorylation and dephosphorylation in spliceosome assembly , and the phosphorylation of SRSFs has been shown to be a prerequisite for spliceosome assembly and splicing . Serine-arginine protein kinases (SRPKs) are a novel subfamily of serine-threonine kinases, which specifically phosphorylate serine residues in the RS domains of SR proteins, affecting SR protein localization and mRNA splicing . The first... ... middle of paper ... ...tiangiogenic SRPK1 inhibitors reduce choroidal neovascularization in rodent models of exudative AMD. Invest Ophthalmol Vis Sci, 2013. 54(9): p. 6052-62.