Adenosine monophosphate transfer

The selection of transformed chloroplasts usually involves the use of an antibiotic resistance marker. Spectinomycin is used most routinely because of the high specificity it displays as a prokaryotic translational inhibitor as well as the relatively low side effects it exerts on plants. The bacterial aminoglycoside 3 -adenyltransferase gene (ciadA) confers resistance to both streptomycin and spectinomycin. The aadA protein catalyzes the covalent transfer of an adenosine monophosphate (AMP) residue from adenosine triphosphate (ATP) to spectinomycin, thereby converting the antibiotic into an inactive form that no longer inhibits protein synthesis for prokaryotic 70S ribosomes that are present in the chloroplast. 

Many of the essential chemicals in life processes are phosphate esters. These include the genetic substances DNA and RNA [representative fragments of the chains appear as (10-XXVII) and (10-XXVIII), respectively] as well as cyclic AMP (adenosine monophosphate), (10-XXIX). In addition, the transfer of phosphate groups between ATP and ADP... 

Figure 3 Biosynthetic pathways. (A) In the terpenoid coupling reaction, isomers of isopentenyl pyrophosphate are joined with the loss of pyrophosphate, leading to a linear intermediate that is cyclized to a terpenoid skeleton, as shown for the diterpene taxol. (B) In the polysaccharide coupling reaction, hexose and pentose monomers are joined with the loss of a nucleoside diphosphate, as shown for the epivancosaminyl-glucose disaccharide of vancomycin. (C) In the first step of the nonribosomal peptide coupling reaction, an aminoacyl adenylate is transferred to a carrier protein or thiolation domain (denoted T ) with loss of adenosine monophosphate. In the second step, this carrier protein-tethered aminoacyl group is coupled to the amine of an aminoacyl cosubstrate, forming a peptide bond, as shown for two residues in backbone of vancomycin. (D) In the polyketide coupling reaction, the loss of carbon dioxide from a two or three-carbon monomer yields a thioester enolate that attacks a carrier protein-tethered intermediate, forming a carbon-carbon bond as shown for the polyketone precursor of enterocin.

Cyclic adenosine monophosphate (cAMP) activates PKA, which in turn phosphor-ylates Cx43 in rat cardiomyocytes.33 Increases in the cAMP concentration increase electrical conductance between paired cardiomyocytes31,34,35 and increase cell permeability - assessed as dye transfer - in non-cardiomyocytes.36 38 Apart from increased cell-cell conductance and permeability, cAMP also increases the extent of gap junction formation.36 38 Increased cAMP concentration results from its enhanced production following stimulation of adenyl cyclase or from inhibition of phosphodiesterase III secondary to an increased concentration of cyclic guanosine monophosphate (cGMP).39-41... 

Cyclic adenosine monophosphate (cAMP) acts as an intermediary in transferring a chemical signal from outside a cell to the metabolic processes inside a cell. 

ATP can transfer energy to another molecule in a variety of ways (Figure 3.10.2). The most common way is the transfer of a phosphate group to the molecule that requires energy (Fogiel, 1999). This reaction liberates adenosine diphosphate (ADP), and is known as a phosphorylation reaction. It is usually catalyzed by enzymes called kinases. If two phosphate groups are transferred, adenosine monophosphate (AMP) remains. 

The hydrolysis of ATP to ADP is the principal energy-releasing reaction for ATP. However, some other hydrolysis reactions also play important roles in energy transfer. An example is the hydrolysis of ATP to adenosine monophosphate (AMP) and pyrophosphate (PP,) ... 

Posttranslational modification (PTM) with functional groups is a universal mechanism for diversifying the activities of proteins. PTMs can affect many properties of proteins, such as localization, activity status, interaction networks, solubility, folding, turnover, or stabUity. It is therefore of vital importance to accurately determine the identities of modified proteins, the modified amino acid residues, and the covalently attached group. This chapter describes the process of PTM identification using the adenylylation (i.e., the covalent transfer of an adenosine monophosphate (AMP)) of rat sarcoma related in brain (Rab) proteins hy Legionella pneumophila enzymes as an example. It also deals with the development of PTM-specific antibodies from synthetic peptides. This account underlines the importance of chemical biology in the elucidation of PTMs. 

The initial step in cytokinin (adenine derivatives with an isoprenoid side chain) biosynthesis is Al-prenylation of adenosine 5-phosphate, a reaction catalyzed by adenosine phosphate-isopentenyltransferases (PTs). PTs catalyze the isopropene unit transfer reaction to an acceptor (adenosine monophosphate, AMP) which serves as a nucleophile. The latter is alkylated by DMAPP to form, by an Sivf2-nucleophilic displacement reaction, a prenylated AMP and pyrophosphate (PP) as products [14, 15]. 

L-Kynurenine obtained from for the degradation of tryptophan is hydroxylated by a KMO homolog encoded by qbsG. The 3-hydroxy-kynurenine could be transam-inated into xanthurenic acid by the QbsB protein. The bifunctional protein QbsL activates xanthurenic acid via its N-terminal AMP (adenosine monophosphate) lig-ase domain, whereas the C-terminal domain of QbsL is responsible for the addition of the methyl group. QbsCDE proteins transfer sulfur from an unknown sulfur donor molecule. The participation and exact role of QbsK, a putative oxidoreductase, was not clear. Quinolobactin was proposed to result from the spontaneous hydrolysis of 8-hydroxy-4-methoxy-2-quinoline thiocarboxylic acid 17 [18]. 

In the second stage, the m-RNA serves as the template for the formation of polypeptide chains at the biosynthesis site (in the ribosomes). The a-aminocarboxylic acids necessary for this are joined by means of their carboxyl groups to transfer RNA (r-RNA), which has a molecular weight of 25,000. The energy necessary for the addition of the a-aminocarboxylic acids is provided by the conversion of adenosine triphosphate to adenosine monophosphate (ATPAMP). A specific enzyme is necessary for the addition of each aminocarboxylic acid to the growing peptide chain, i.e., at least 20 different enzymes are necessary ... 

The need for energy by the cell regulates the tricarboxylic acid cycle, which acts in concert with the electron transfer chain and the ATPase to produce adenosine triphosphate in the inner mitochondrial membrane. The cell has limited amounts of ATP, adenosine diphosphate (ADP), and adenosine monophosphate (AMP). When ADP levels are higher than ATP, the cell needs energy, and hence NADH is oxidized rapidly and the tricarboxylic acid cycle is accelerated. When the ATP level is higher than ADP, the cell has the energy needed hence, the electron transport chain slows down. 

As shown in Scheme 12.71, and as affirmed by labeling experiments, an amino acid (shown using phenylalanine [Phe, F] as an example in the scheme) to be added to the growing peptide (protein) chain is activated for reaction by attachment at the carboxylate to adenosine triphosphate (ATP) to make an anhydride of the amino acid with adenosine monophosphate (and the loss of inorganic phosphate). Then, in the next step, the activated amino acid is esterified by the C-2 or the C-3 hydroxyl of a ribosyl unit of AMP, which is attached via phosphate at the 5 carbon to the aminoacyl transfer end of tRNA. If attachment is to C-2, rearrangement to C-3 follows and the aminoacyl-tRNA is activated and ready to be added to the growing peptide chain at the synthesis site on the ribosome. 

The diammonium salt of (28) exhibits a remarkable pH-dependent high selectivity, by a factor of up to 30, toward the binding of adenosine diphosphate compared with that of adenosine monophosphate. Compound (28) acts as a typical phase transfer reagent rather than as a micellar reagent. ... 

Fig. 12.22 Structures of calix[4]pyrroles 33, 34, and 35 above). Representation of the transfer of Pt(ll) center from 33 to adenosine monophosphate (AMP)...

Concerning the activation of amino acids for constructing the peptide bond, the folloiving process has been elucidated (Fig. 3). The first step is the formation of adenosine monophosphate of an amino acid (aminoacyl-AMP) by the reaction of an amino acid and adenosine triphosphate (ATP) catalyz by aminoacyl-tRNA synthase (ARS). The resulting aminoacyl-AMP is further attacked by a hydroxyl group of a specific transfer RNA giving rise to an aminoacyl-tRNA as a precursor for the peptide bond formation. 

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