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The original 32P-postlabeling method developed by Randerath and his colleagues has been modified to detect a single type of adduct as a single spot in thin-layer chromatography (TLC), because some types of adducts gave multiple adduct spots by the original method. In the remodified methods, DNA is first digested with micrococcal nuclease and phosphodiesterase II and then labeled with [γ-32P]ATP under standard or adduct intensification conditions. Since the labeled digest includes adducted mono-, di-, and/or oligo-deoxynucleotides, it is further treated with phosphatase and phosphodiesterase prior to TLC. The labeled digest is treated with nuclease P1 (NP1) in Method I, with T4 polynucleotide kinase and NP1 in Method II, and then with phosphodiesterase I in both cases and subjected to TLC. The advantage of these methods is that the number of adduct species formed can be estimated by TLC. [ABSTRACT FROM AUTHOR]

Posttranslational processes are essential for generation and dynamics of circadian rhythms in species as diverse as cyanobacteria and human. Historically, circadian rhythm generation at the molecular level was thought to be primarily based on a transcriptional-translational feedback loop, in which negative components inhibit the transcriptional activity of their own activators. Subsequently, it has been increasingly recognized that – beyond negative transcriptional control – concepts such as delay or cooperativity are required to generate oscillations. The last few years have witnessed enormous progress in our understanding of how posttranslational events are involved in these essential steps. For example, phosphorylation and dephosphorylation of clock proteins not only fine-tunes stability and subcellular localization but may also regulate complex formation and transcriptional activity. In addition, acetylation, sumoylation, and ubiquitination of clock proteins also turned out to be important for normal circadian rhythms. Here, we review our current knowledge of these processes and their impact on circadian rhythms in mammals. [ABSTRACT FROM AUTHOR]

Cyanobacterial diversity is reviewed to provide background knowledge for researchers concerned with cyanobacterial toxins and toxicity, with emphasis on ecological, morphological and physiological aspects. Ways in which the environment influences cyanobacterial morphology on evolutionary and short-term time-scales are assessed, because lack of understanding about this underlies some of the muddle in current taxonomic approaches. The review then deals with how cyanobacteria respond to their environment, including sensing, N versus P limitation, some less well recognized aspects of P limitation and responses to grazers. The importance of considering flowing water and other types of envirponment besides lakes and reservoirs is stressed. Comment on interactions between cyanobacteria and other organisms includes mention of the use of barley straw in controlling blooms, an approach which has often proved successful in the British Isles and elsewhere in Europe, but less so in the USA. The review ends with how the environment influences toxin production and toxicity of the toxins released. Several topics are suggested where there is a need for research, such as whether the calyptra of some Oscillatoriaceae has a role in sensing the environment, and whether some rice cultivars produce straw useful for controlling blooms. [ABSTRACT FROM AUTHOR]

An encyclopedia entry for phosphodiesterases is presented. Phosphodiesterases are a class of enzymes that catalyze the hydrolysis of 3',5'-cyclic guanosine monophosphate to 5'-guanosine monophosphate. The basic characteristics of phosphodiesterases are discussed, including their substrate specificity and regulatory domains. In addition, this entry discusses the compartmentalization of phosphodiesterases.

The article presents an encyclopedia entry on the definition of the term "GTPase." The term, also known as guanosine triphosphatase (GTP)-binding proteins, G-proteins or small GTP-binding proteins are members of the Ras superfamily. They are enzymes that catalyzes the hydrolysis of GTP to guanosine 5'-diphosphate and inorganic phosphate.

A definition of the term "phosphatases" is presented. It refers to enzymes that are responsible for the removal of phosphate groups from proteins. They are responsible for shutting down signaling pathways in a cell.

A definition of the term "phosphorylative balance" is presented. It is a descriptor of the status maintained by cellular proteins as a result of the activities of cellular phosphatases and kinases.

A definition of the term "vav proteins" is presented. These protein are guanine nucleotide exchange factors (GEF) for monomeric GTPases. The Vav proteins belong to the DBL family of Rho GEF and have a significant role in regulating early events in receptor signalling.

A definition of the term "vacuolar-type proton translocating ATPase" is presented. It refers to a hetereomeric protein complex which appears to translocate two protons across the vesicle membrane for each ATP molecule that is hydrolyzed, generating chemical and electrical gradients.

A definition of the term "PTEN" is presented. It refers to a phosphatase which is a product of a tumor suppressor gene. It has a unusually broad specificity and can remove phosphate groups attached to serine, threonine and tyrosine residues. Dephosphorylate phosphatidylinositol is responsible for its tumor suppressor effects.

An encyclopedia entry for phospholipid phosphatases is presented. They are enzymes such as SHz-domain containing inositide-5-phosphatase or phosphatase and tensin homolog deleted on chromosome 10 or PTEN which dephosphorylate phosphoinositides. PTEN has opposite effects to phosphatidylinositol 3-kinases and is considered to be a tumor suppressor.

An encyclopedia entry for phosphatases is presented. A phosphatase is an enzyme that hydrolyzes phosphomonoesterases. Phospholipids and proteins are the substrates for phosphatases. A wide variety of protein phosphatases exist and are generally classified according to their substrate specificities.

An encyclopedia entry for "myosin phosphatase," is presented. It contains a 110-130 kD myosin phosphatase targeting and regulatory subunit, a 37 kD catalytic subunit and a 20 kD subunit of unknown function.

An encyclopedia entry for the term "lipid phosphate phosphohydrolases" is presented. It is formerly called type 2 phosphatidate phosphohydrolases. It catalyses the dephosphorylation of bioactive phospholipids and lysophospholipids. They are also characterized by a lack of requirement for magnesium2+ and insensitivity to N-ethyl-maleimide.

A reference entry for the abbreviation "PTPN13," which stands for protein tyrosine phosphatase non-receptor type 13, is presented. It is also known as APO-1/ CD95/Fas-associated phosphatase and the gene locus maps to 4q21.

A definition of the term "phosphatase" is presented. It refers to a specialized protein possessing enzymatic activity that catalyzes the removal of phosphate groups from amino acids, nucleic acid, fatty acids or sugars. A phosphatase also has the opposite effect to a kinase.

A definition of the term "dynamin," which refers to a guanosine triphosphatase capable of self-assembling into oligomeric collars around the necks of coated pits is presented.

A definition of the term "CDC25A" is presented. It refers to cell division cycle 25A. It is a is a M-phase inducer phosphatase 1 of 523 amino acids and 58 kD. It functions as a dosage-dependent inducer in mitotic control. CDC25A is a tyrosine protein phosphatase required for progression of the cell cycle.

A definition of the term "CD45" is presented. It is also known as leukocyte common antigen. CD 45 is a a family of protein tyrosine phosphatases expressed exclusively on the surface of almost all hematolymphoid cells and their progenitors.