Polypeptides translation

Laurell and coworkers have identified an alternatively spliced shorter (80 kDa) form of human HSL that is exclusively expressed in WAT and devoid of both esterase and lipase activities, and is presumably generated by skipping of exon 6, which encodes fhe serine residue of the catalytic triad [295]. Subsequenfly, two HSL immunoreactive bands (88 kDa = L form and 84 kDa = S form) in homogenates from human obese adipose tissue were reported [296]. Immunodetection experiments with an antibody specifically recognizing the domain encoded by exon 6 suggested fhat fhe 80 kDa and S forms correspond to the polypeptide translated... 

E. Schroder and K. Lxibke, The Peptides, Synthesis, Occiarrence, and Action of Biologically Active Polypeptides. Translated by E. Gross. Academic Press Inc., Ill Pith Avenue, New York, New York, I966. 

The fourth FMD virus capsid polypeptide translated has been designated VP3, VPl, or VPthr, due to its variable migration in different polyacrylamide gel electrophoresis systems. This protein will be referred to as VPl as recommended at the 1982 American Society of Virology meeting at Ithaca, NY. 

BOIME, I. and LEBER, P. Protein synthesis directed by EMC virus RHA. III.Biscrete polypeptides translated from a monocistronic messenger in vitro. Arch. Biochem. Biophys. 

Maeeenger RNA, mRNA, template RNA RNA which is translated into a polypeptide on the ribosome (see Protein biosynthesisy One molecule of mRNA may carry information for the synthesis of more than one protein, having been transcribed without interruption from several neighboring cistrons of the DNA. This polycistronic mRNA has so far been found only in prokaryotes. The polypeptides translated from polycistronic mRNA usually have related functions, e.g. 10 enzymes of histidine biosynthesis are encoded in and translated from a polycistronic mRNA containing about 12,000 nucleotides, M, 4 x 10. Viral RNA is functionally very similar to mRNA. The entire length of viral RNA or mRNA is not translated, the start codon (always AUG) is located some distance in from the 5 -end of the molecule. For example, the start codon for p-galactosidase in the Lac mRNA of E. coli occurs at position 39. The untranslated sequence of nucleotides at the S -end of prokaryotic mRNA includes nucleotides complementary to a sequence in the 16S rRNA of the ribosome and this is believed to help bind the mRNA to the ribosome. 

Now let us look at translation, the path from mRNA to completed polypeptide. Translation is a more complicated process than transcription. The most important factors needed in a system for translation are the following ... 

For example, a polypeptide is synthesized as a linear polymer derived from the 20 natural amino acids by translation of a nucleotide sequence present in a messenger RNA (mRNA). The mature protein exists as a weU-defined three-dimensional stmcture. The information necessary to specify the final (tertiary) stmcture of the protein is present in the molecule itself, in the form of the specific sequence of amino acids that form the protein (57). This information is used in the form of myriad noncovalent interactions (such as those in Table 1) that first form relatively simple local stmctural motifs (helix... 

Fig. 2. Protein secondary stmcture (a) the right-handed a-helix, stabilized by intrasegmental hydrogen-bonding between the backbone CO of residue i and the NH of residue t + 4 along the polypeptide chain. Each turn of the helix requires 3.6 residues. Translation along the hehcal axis is 0.15 nm per residue, or 0.54 nm per turn and (b) the -pleated sheet where the polypeptide is in an extended conformation and backbone hydrogen-bonding occurs between residues on adjacent strands. Here, the backbone CO and NH atoms are in the plane of the page and the amino acid side chains extend from C ...

The shell of all picomaviruses is built up from 60 copies each of four polypeptide chains, called VPl to VP4. These are translated from the viral RNA into a single polypeptide, which is posttranslationally processed by stepwise proteolysis involving viraily encoded enzymes. First, the polypeptide chain is cleaved into three proteins VPO (which is the precursor for VP2 and VP4), VPl and VP3. These proteins begin the assembly process. The last step of the processing cascade occurs during completion of the virion assembly the precursor protein VPO is cleaved into VP2 and VP4 by a mechanism that is probably autocatalytic but may also involve the viral RNA. VPl, VP2, and VP3 have molecular masses of around 30,000 daltons, whereas VP4 is small, being 7000 daltons, and is completely buried inside the virion. 

Figure 18.12 The electron-density map is interpreted by fitting into it pieces of a polypeptide chain with known stereochemistry such as peptide groups and phenyl rings. The electron density (blue) is displayed on a graphics screen in combination with a part of the polypeptide chain (red) in an arbitrary orientation (a). The units of the polypeptide chain can then be rotated and translated relative to the electron density until a good fit is obtained (b). Notice that individual atoms are not resolved in such electron densities, there are instead lumps of density corresponding to groups of atoms. [Adapted from A. Jones Methods Enzym. (eds. H.W. Wyckoff, C.H. Hirs, and S.N. Timasheff) 115B 162, New York Academic Press, 1985.]...

Messenger RNA (mRNA) serves to carry the information or message that is encoded in genes to the sites of protein synthesis in the cell, where this information is translated into a polypeptide sequence. Because mRNA molecules are transcribed copies of the protein-coding genetic units that comprise most of DNA, mRNA is said to be the DNA-like RNA. ... 

Ribosomal RNAs characteristically contain a number of specially modified nucleotides, including pseudouridine residues, ribothymidylic acid, and methylated bases (Figure 11.26). The central role of ribosomes in the biosynthesis of proteins is treated in detail in Chapter 33. Here we briefly note the significant point that genetic information in the nucleotide sequence of an mRNA is translated into the amino acid sequence of a polypeptide chain by ribosomes. 

Glycosydphosphatidylinositolation The GlycoPho-sphatidyl Inositol moiety anchor of AChE consists exclusively of diacyl molecular species. Over 85% of the molecular species are composed of palmitoyl, stearoyl and oleoyl. The post-translational process of glypiation takes place in the endoplasmic reticulum, after completion of the polypeptide chain the newly synthesized protein interacts with a transamidase... 

Both the heat and cold shock response are universal and have been studied extensively. The major heat shock proteins (HSPs) are highly conserved. They are involved in the homeostatic adaptation of cells to harsh environmental conditions. Some act as molecular chaperones for protein folding, while others are involved in the processing of denatured polypeptides whose accumulation would be deleterious. The cold shock results in the transient induction of cold shock proteins (CSPs), which include a family of small acidic proteins carrying the cold shock domain. The CSPs appear to be involved in various cellular functions such as transcription, translation and DNA recombination. 

After mRNA splicing, the tropoelastin mRNA is translated at the surface of the rough endoplasmic reticulum (RER) in a variety of cells smooth muscle cells, endothelial and microvascular cells, chondrocytes and fibroblasts. The approximately 70 kDa precursor protein (depending on isoform) is synthesized with an N-terminal 26-amino-acid signal peptide. This nascent polypeptide chain is transported into the lumen of the RER, where the signal peptide is removed cotranslationally [9]. 

Finally, to produce the structural and functional devices of the cell, polypeptides are synthesized by ribosomal translation of the mRNA. The supramolecular complex of the E. coli ribosome consists of 52 protein and three RNA molecules. The power of programmed molecular recognition is impressively demonstrated by the fact that aU of the individual 55 ribosomal building blocks spontaneously assemble to form the functional supramolecular complex by means of noncovalent interactions. The ribosome contains two subunits, the 308 subunit, with a molecular weight of about 930 kDa, and the 1590-kDa 50S subunit, forming particles of about 25-nm diameter. The resolution of the well-defined three-dimensional structure of the ribosome and the exact topographical constitution of its components are still under active investigation. Nevertheless, the localization of the multiple enzymatic domains, e.g., the peptidyl transferase, are well known, and thus the fundamental functions of the entire supramolecular machine is understood [24]. 

Figure 38-5. Examples of the effects of deletions and insertions in a gene on the sequence of the mRNA transcript and of the polypeptide chain translated therefrom. The arrows indicate the sites of deletions or insertions, and the numbers in the ovals indicate the number of nucleotide residues deleted or inserted. Blue type indicates amino acids in correct order.

A number of polypeptide biomarkers have also been identified in the mass range below 4000,28-31 which are cyclic secondary metabolites bonded to lipids or sugars. These peptide sequences are not directly translated from DNA,32... 

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