Phosphorylation in bacteria

Phosphorylation in bacteria. A bacterial enzyme whose activity is controlled by phosphorylation is isocitrate dehydrogenase. Transfer of a phospho group to the - OH of Ser 113 completely inactivates the... 

Deutscher J, Saier MHJ (2005) Ser/Thr/Tyr protein phosphorylation in bacteria— for long time neglected, now well established. J Mol Microbiol Biotechnol 9 125-131... 

Although the schemes presented in Fig. 4 represent one important mechanism of coupling substrate oxidation with phosphorylation in bacteria, other mechanisms may occur also. In higher animals, phosphotransacetylase and phosphotranssuc-cinylase appear to be absent. In these organisms, therefore, the acyl-SCoA derivatives formed in the oxidation of pyruvate and a-ketoglutarate are used to synthesize ATP by mechanisms that do not involve the intermediate formation of acyl phosphate. ATP formation from acetyl-SCoA (11) appears to occur by reactions (1), (2), and (3), whereas the synthesis of ATP from succinyl-SCoA occurs by an as yet undetermined pathway (15). 

To understand the mechanism of photosynthetic energy transformation, complete knowledge of the components involved is essential. To study the photosynthetic ATPsynthase, resolution and reconstitution experiments have been carried out now for 20 years (Avron,1963). Numerous details and analogies to the ATPsyntha-ses of oxidative phosphorylation in bacteria and mitochondria have been elucidated (Munoz,1982). 

Histidine phosphatases and aspartate phosphatases are well established in lower organisms, mainly in bacteria and in context with two-component-systems . Reversible phosphorylation of histidine residues in vertebrates is in its infancy. The first protein histidine phosphatase (PHP) from mammalian origin was identified just recently. The soluble 14 kD protein does not resemble any of the other phosphatases. ATP-citrate lyase and the (3-subunit of heterotrimeric GTP-binding proteins are substrates of PHP thus touching both, metabolic pathways and signal transduction [4]. 

II cleaves the two complementary strands of DNA four base pairs apart and the resulting 5 -phosphoryl groups become covalently linked to a pair of tyrosine groups, one in each half of the dimeric topoisomerase II enzyme. Several groups of drugs are known that selectively inhibit topoisomerases in bacteria (quino-lones) or mammalian cells (etoposide, tenoposide). Quinolones are used to treat bacterial infections inhibitors of mammalian topoisomerases are cytostatic drugs used for the treatment of cancer. 

The reaction of X with S must be fast and reversible, close to if not at equilibrium with concentration of S. It can be that there is an intermediate step in which X binds to a protein kinase (a protein which phosphorylates other proteins mostly at histidine residues in bacteria) using phosphate transferred from ATP. It then gives XP which is the transcription factor, where concentration of S still decides the extent of phosphorylation. No change occurs in DNA itself. Here equilibrium is avoided as dephosphorylation involves a phosphatase, though changes must be relatively quick since, for example, cell cycling and division depend on these steps, which must be completed in minutes. We have noted that such mechanical trigger-proteins as transcription factors are usually based on a-helical backbones common to all manner of such adaptive conformational responses (Section 4.11). 

It has recently been shown that some phosphorylations may be useful only to activate a protein and once in its active form or complexed, phosphorylation is no longer needed (Scheme 3). Karwowska-Desaulniers et ak recently hypothesized that phosphorylation of histone deacetylase 1 (HDACl) at two key residues is important for complex formation of active protein in vivo. However, when the phosphorylation sites were mutated to alanine, no active protein was expressed, yet complex formation was still observed. Even when native protein was expressed and dephosphorylated, complex formation and activity were still observed. The complex formation is still not fully understood the complexes are thought to place HDAC in the correct position. No active noncomplexed HDAC has been generated in order to study the effects of complexation. Interestingly, when HDACl was expressed in bacteria and subsequently phosphorylated there was no... 

Post-translational modifications, such as phosphorylation, complex glycosylation, and lipidation, typically occur in eukaryotic organisms. Therefore, their expression in prokaryotic systems like Escherichia coli is difficult. However, it should be noted that via clever engineering and coexpression of specific enzymes, access can be granted to specific lipidated proteins via expression in bacteria, for example, via the expression of A -myristoyltransferase in E. coli Eukaryotic systems that can be used for the expression of post-translationally modified proteins are yeast and Dictyostelium discoidum. Furthermore, lipidated proteins, such as the Rah proteins, can be obtained via purification from tissue sources or from membrane fractions of insect cells that had been infected with baculovirus bearing a Rah gene. ... 

One kind of active transport, namely group translocation, occurs in bacteria (for reviews, see Refs. 218-223), and some workers consider that this also takes place in yeasts (see, for example, Refs. 224 and 225) by this means, uptake of a sugar is directly coupled to its phosphorylation, and the sugar is released into the cytoplasm as a phosphate. 

Various signaling systems used by animal cells also have analogs in the prokaryotes. As the full genomic sequences of more, and more diverse, bacteria become known, researchers have discovered genes that encode proteins similar to protein Ser or Thr kinases, Ras-like proteins regulated by GTP binding, and proteins with SH3 domains. Receptor Tyr kinases have not been detected in bacteria, but (P)-Tyr residues do occur in some bacterial proteins, so there must be an enzyme that phosphorylates Tyr residues. 

DNA contains thymine rather than uracil, and the de novo pathway to thymine involves only deoxyribonu-cleotides. The immediate precursor of thymidylate (dTMP) is dUMP. In bacteria, the pathway to dUMP begins with formation of dUTP, either by deamination of dCTP or by phosphorylation of dUDP (Fig. 22-43). The dUTP is converted to dUMP by a dUTPase. The latter reaction must be efficient to keep dUTP pools low and prevent incorporation of uridylate into DNA. 

The oxidative processes of cells have been hard to study, largely because the enzymes responsible are located in or on cell membranes. In bacteria the sites of electron transport and oxidative phosphorylation are on the inside of the plasma membrane or on membranes of mesosomes. In eukaryotes they are found in the inner membranes of the mitochondria and, to a lesser extent, in the endoplasmic reticulum. For this reason we should probably start with a closer look at mitochondria, the "power plants of the cell."... 

Due to its central role in oxidative phosphorylation, cytochrome oxidase has a wide biological distribution. It is present in all animals and plants, in aerobic yeasts and in some bacteria. It is an integral membrane protein, being firmly associated with the inner membrane of mitochondria, the respiratory organelle of eukaryotic organisms, or, in bacteria the plasma membrane (Malstrom, 1990). 

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