Proteins cellular information transfer from

Figure 24. Illustration of hase-pair analogues effector conception (26, 97, 98, 99, 100). Survey on simplified schemes of carho- and heteroaromatic systems (a) (preceding page) cytokinines (b) (this page, top) steroids (c) (this page, bottom) and structural analogues and differently shaped, effectors (d) (following page) of cellular information transfer from nucleic acids to protein.

Fig. 5. Molecular information transfer from DNA to cellular protein during bio-cellular network development...

The site of synthesis of numerous proteins is remote from their site of function. During transfer from one site to the other, proteins must, therefore, cross cellular membranes [43] [44], Proteins are usually synthesized as precursors containing an amino terminal extension, called the signal (leader) peptide, the sequence of which contains the necessary information to guide the protein to and across a specific membrane. After transmembrane transport (called translocation), the signal peptide is cleaved off by specific signal peptidases, which are found in the rough endoplasmic reticulum, and the... 

The central dogma of molecular biology is that information is transferred from DNA to RNA to proteins. The proteins (which include the enzymes and structural components of cells) are directly responsible for most cellular activities and functions. The information needed for all functions of all organisms is stored in the genomic DNA sequence, which contains discrete units defined as genes. Each gene encodes a protein whose function and activity are determined by its primary sequence. The discovery of colinearity of the DNA nucleotide sequence and the amino acid sequence of the encoded polypeptide in prokaryotes and their viruses led to the discovery of the genetic code... 

Not all the cellular DNA is in the nucleus some is found in the mitochondria. In addition, mitochondria contain RNA as well as several enzymes used for protein synthesis. Interestingly, mitochond-rial RNA and DNA bear a closer resemblance to the nucleic acid of bacterial cells than they do to animal cells. For example, the rather small DNA molecule of the mitochondrion is circular and does not form nucleosomes. Its information is contained in approximately 16,500 nucleotides that func-tion in the synthesis of two ribosomal and 22 transfer RNAs (tRNAs). In addition, mitochondrial DNA codes for the synthesis of 13 proteins, all components of the respiratory chain and the oxidative phosphorylation system. Still, mitochondrial DNA does not contain sufficient information for the synthesis of all mitochondrial proteins most are coded by nuclear genes. Most mitochondrial proteins are synthesized in the cytosol from nuclear-derived messenger RNAs (mRNAs) and then transported into the mito-chondria, where they contribute to both the structural and the functional elements of this organelle. Because mitochondria are inherited cytoplasmically, an individual does not necessarily receive mitochondrial nucleic acid equally from each parent. In fact, mito-chondria are inherited maternally. 

In prokaryotes DNA, RNA, and protein synthesis all take place in the same cellular compartment. In eukaryotes the DNA is compartmentalized in the cell nucleus, and it became clear long before the biochemistry of these three processes was understood that DNA synthesis takes place in the nucleus, whereas the bulk of protein synthesis takes place in the cytoplasm. From these observations on eukaryotes it was self-evident that DNA cannot be directly involved in the synthesis of protein but must somehow transmit its genetic information for protein synthesis to the cytoplasm. Careful experiments with radioactive labels were used to demonstrate that RNA synthesis takes place in the nucleus much of this RNA is degraded rather quickly, but the portion that survives is mostly transferred to the cytoplasm (fig. 28.1). From observations of this kind it became clear that RNA was the prime candidate for the carrier of genetic information for the synthesis of proteins. 

Signal transduction involves a transfer of information from cell surface receptors to the cytoplasm and ultimately to the nucleus where cellular activation and response are initated (1). Protein-tyrosine kinases (PTKs) serve central roles in many of these pathways by phosphorylating tyrosyl residues, which result in the introduction of phosphotyrosyl (pTyr, 1, Fig. 1) pharmacophores... 

The flow of genetic information in normal cells is from DNA to RNA to protein. The synthesis of RNA from a DNA template is called transcription, whereas the synthesis of a protein from an RNA template is termed translation. Cells contain several kinds of RNA messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA), which vary in size from 75 to more than 5000 nucleotides. All cellular RNA is synthesized by RNA polymerase according to instructions given by DNA templates. The activated intermediates are ribonucleoside triphosphates and the direction of... 

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