Proteins synthesizing

Biological catalysts — enzymes — are usually proteins. The development of new protein syntheses is nowadays dominated by genetic protein engineering (see section 4.1.2.6). Bio-organic approaches towards novel catalytically active structures and replicating systems try to manage without biopolymers. 

Many protective groups have been developed for the amino group, including carbamates (>NCO,R), used for the protection of ammo acids in peptide and protein syntheses, and amides (>NCOR). used more widely in syntheses of alkaloids and for the protection of the nitrogen bases adenine, cytosine, and guanine in nucleo-... 

Ribosomes, the protein-synthesizing machinery of cells, are composed of two subunits, called small and large, and ribosomal RNAs are integral components of these subunits (see Table 11.2). A large degree of intrastrand sequence com-... 

The term vitamin E describes a family of eight antioxidants, four tocopherols, alpha (a), beta ((3), gamma (y) and delta (8), and four tocotrienols (also a, (3, y, and 8). a-Tocopherol is present in nature in only one form, RRR a-tocopherol. The chemical synthesis of a-tocopherol results in eight different forms (SRR, SSR, SRS, SSS, RSR, RRS, RSS, RRR), only one of which is RRR a-tocopherol. These forms differ in that they can be right (R) or left (S) at three different places in the a-tocopherol molecule. RRR a-tocopherol is the only form of vitamin E that is actively maintained in the human body and is therefore the form of vitamin E found in the largest quantities in the blood and tissue. A protein synthesized in the liver (a-TTP alpha-tocopherol transfer protein) preferentially selects the natural form of vitamin E (RRR a-tocopherol) for distribution to the tissues. However, the mechanisms for the regulation of vitamin E in tissues are not known... 

Aldashev, A.A., Agibetov, K.A., Yugai, A.A., Shamshiev, A.T. (1991). Specific proteins synthesized in human lymphocytes during hypoxia. Am. J. Physiol. 261, S92-96. 

This has a distinct isotopic consequence for the composition of proteins synthesized from these amino acids. To the extent that FAs differ isotopically from the remainder of the diet, this difference is under-represented in proteins partly built up of AAs that caimot be synthesized from an FA precursor. We could represent this difference by a ratio rf, the fraction ofFA-derived C atoms in the AA pool from which proteins are made, divided by the fraction of FA-derived C atoms in the total diet. 

Comparison of the model-derived DIFF with the experimentally evaluated DIFF show that protein routing can be described in terms of the amount of protein synthesized from catabolic activity that is, in general it is around 20% of the mean carbon flux of the diet. A simple explanation why dp > dw is also proposed. 

A number of complex molecules such as proteins have been incorporated into the polyanhydrides, including insuhn, enzymes, chon-drogenic stimulating proteins, and a protein synthesized by genetic engineering techniques. 

Those cytoplasmic RNA molecules that serve as templates for protein synthesis (ie, that transfer genetic information from DNA to the protein-synthesizing machinery) are designated messenger RNAs, or mRNAs. Many other cytoplasmic RNA molecules (ribosomal RNAs rRNAs) have strucmral roles wherein they con-... 

This class is the most heterogeneous in size and stability. All members of the class function as messengers conveying the information in a gene to the protein-synthesizing machinery, where each serves as a template on which a specific sequence of amino acids is polymerized to form a specific protein molecule, the ultimate gene product (Figure 35-9). 

A major sorting decision is made early in protein biosynthesis, when specific proteins are synthesized either on free or on membrane-bound polyribosomes. This results in two sorting branches called the cytosolic branch and the rough endoplasmic reticulum (R R) branch (Figure 46-1). This sorting occurs because proteins synthesized on membrane-bound polyribosomes contain a signal peptide that mediates their attachment to the membrane of the ER. Further details on... 

The signal hypothesis was proposed by Blobel and Sabatini pardy to explain the distinction between free and membrane-bound polyribosomes. They found that proteins synthesized on membrane-bound polyribosomes contained a peptide extension (signal peptide)... 

Most proteins that are synthesized on membrane-bound polyribosomes and are destined for the Golgi apparatus or plasma membrane reach these sites inside transport vesicles. The precise mechanisms by which proteins synthesized in the rough ER are inserted into these vesicles are not known. Those involved in transport from the ER to the Golgi apparatus and vice versa—and from the Golgi to the plasma membrane— are mainly clathrin-free, unlike the coated vesicles involved in endocytosis (see discussions of the LDL receptor in Chapters 25 and 26). For the sake of clarity, the non-clathrin-coated vesicles will be referred to in... 

Many proteins synthesized on membrane-bound polyribosomes proceed to the Golgi apparatus and the plasma membrane in transport vesicles. 

Fig. 1. Reconstruction of the cell-free protein synthesizing system with the partially purified wheat germ extracts. Control normal wheat germ cell-free system, (I) 0 - 40 % ammonium sulfate fraction 3 pi, 40 - 60 % ammonium sulfate fraction 4 pi, and ribosome 3 pi were added to 25 pi reaction mixture, (II) 0-40 % ammonium sulfate fraction 4 pi, 40 - 60 % ammonium sulfate fraction 4 pi, and ribosome 1.5 pi were added to 25 pi reaction mixture.

Bacteria are vulnerable to the selective attack of chemotherapeutic agents because of the many metabolic and molecular differences between them and animal cells. The biology of vims replication, with its considerable dependence on host-cell energy-producing, protein-synthesizing and biosynthetic enzyme systems, severely limits the opportunities for selective attack. Another problem is that many vims diseases only become apparent after extensive viral multiplication and tissue damage has been done. 

RNA Ribonucleic acid Transfers genetic information from DNA to proteins synthesized by the cell... 

The total proteins synthesized by bacteria grown under standard conditions, when analyzed by polyacrylamide gel electrophoresis (PAGE), form patterns that can be compared to those of known strains by visual or computer-assisted... 

All together, 12 clotting factors are in the plasma. These factors, which are proteins synthesized in the liver, are normally found circulating in plasma... 

Viral proteins Once mRNA is made, viral proteins (for example, enzymes, capsomers) can be synthesized. The proteins synthesized as a result of virus infection can be grouped into two broad categories,... 

Even the genes that code for proteins are more complex in vertebrates than in bacteria. Most, but not all, are expressed as long RNA molecules that are reduced in size by splicing together the coding segments. This yields a continuous template RNA that is sequentially decoded by protein-synthesizing enzymes. 

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