How are GTPases regulated and how do they affect their effectors?
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http://en.wikipedia.org/wiki/GTPase
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GGT has to do with protein synthesis. In terms of steroid use, they increase synthesis. Just a side effect.
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mitochondria, golgi apparatus, endoplasmic reticulum (smooth or rough)
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Signal molecules are often called ligands, and they bind to receptors on the outside of cells.  The proteins (or glycoproteins) that we call receptors are membrane bound proteins (like a G-protein coupled receptor.  So, ligands (like a hormone) bind reversibly to these receptors, and begin the G-Protein signaling cascade.  After stimulating the receptor, they are simply knocked off or fall off.\n\nWhen a ligand stimulates a G-Protein coupled receptor, the receptor changes conformation, allowing it to associate with a 3-unit (trimeric) G-Protein.  The alpha unit of the G-protein interacts with the receptor, and changes, where a bound GDP is replaced by a GTP molecule.  The G-protein/GTP complex then activates a protein called adenylyl cyclase, which converts free cytoplasmic ATP into cAMP (cyclic AMP).  The cAMP then activates PROTEIN KINASES, which in turn activate transcription factors, initiating transcription of some final gene product.\n\nLet me give you an example.  Fight or flight response, the body needs extra glucose to give to muscle cells, the heart, the brain, etc . . . the sympathetic system is activated, and the adrenal gland releases epinephrine.  Epi then circulates where in liver cells, it binds to a G-Protein coupled receptor called a Beta-adrenergic receptor (adrenergic always refers to a receptor that epinephrine binds to).  The receptor interacts with a G-Protein, the G-protein complexes with GTP, the GTP/G-protein complex activate adenylyl cyclase, ATP is converted to cAMP, transcription factors are activated, proteins that lead to glucose production are transcribed and translated.  As a result, more glucose is released into the bloodstream for skeletal muscle to use as energy.\n\nThis is just one example of how a G-Protein works, there are others, but this gives you a basic idea of cell signaling.  Cell signaling is EVERYWHERE, it is very important to understand it.
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"Upregulation is the process by which a cell increases the number of receptors to a given hormone or neurotransmitter to improve its sensitivity to this molecule. A decrease of receptors is called downregulation."\n\n\n"Upregulation: An increase in the number of receptors on the surface of target cells, making the cells more sensitive to a hormone or another agent. For example, there is an increase in uterine oxytocin receptors in the third trimester of pregnancy, promoting the contraction of the smooth muscle of the uterus."
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well it depend on the species of animal or plant you're studying. in Mammalian cells, The protein mTOR is a serine/threonine kinase that regulates DNA translation and cell division. the availability of a food source for the cell influences mTOR so that when cells are not able to grow to normal size they will not go through cell division. This is just one of the proteins synthesized during different times of a cell cycle to prevent mitosis from occuring. some disrupt the formation of mitotic spindles, some prohibit the cell from going into prophase or metaphase...others work on chemical receptors and hormones released form the cell. google search it, and I hope this has helped :)
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Cancer, in laymans's terms, is the unregulated growth of a cell.  Now cell growth, and activities in general, are typically regulated through cell receptors which, in response to a stimulus, activate or release a kinase.  These kinases transfers phosphates to other proteins or phosphorylates them making them active to stimulate DNA replication and transcription (growth).  Cancer is commonly characterized by high levels of (active) kinase due to suppressed phosphotase activity (opposite of a kinase) or defective oncoreceptors stuck in the "ON" position.
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Active and passive. Effectors change the function of the allosteric enzymes, and can make enzymes either active (allosteric activation) or passive (allosteric inhibition).
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Wee1 is a kinase which inhibits cdc2/cdk1 kinase activity, via phosphorylation at Y15.  This residue is dephosphorylated by Cdc25C phosphatase and allows entry into mitosis (or meiotic progression).  It's so called because S Pombe mutants became 'wee' or small due to the mutation of this gene, implying it's role in the cell cycle (specifically mitosis).  \n\nIt's discussed in most cell biology texts.\nie here\nhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=wee1+AND+mcb%5Bbook%5D+AND+106201%5Buid%5D&rid=mcb.section.3496#3501
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Inside our cells -it is a blind, mute and deaf world of roaming/floating molecules! Molecules (including the macromolecules like proteins) wonder almost aimless but can have influence on each other -like, breaking or joining others. But these interactions have to specific. The specific contact and the influence on each other is possible only due to the compatibility in the physico-chemical features on their surfaces, which are directly dependent on the structure.\n\nIt is the proteins that carry out most of the functions in cells. Hence, protein structure is very important for cell function. Because actin is such a basic structural protein and cytochalasin B can interact with it (and affect it), their interactions seem influence activities in different cells and events like fertilization and immune functions. You can look up for literature on this aspect.\n\nI am quoting one abstract from the NCBI's PubMed database (Journal -Biochim Biophys Acta. 1980 Dec 16;626(2):494-500.; PMID: 6894243)of research work by  Maruyama K, Hartwig JH &Stossel TP.:\n\nCytochalasin B and the structure of actin gels. II. Further evidence for the splitting of F-actin by cytochalasin B.\nCytochalasin B decreased the flow birefringence and s20,w and increased the extinction angle of actin filaments in salt solutions favoring polymerization of the protein. These changes occurred without a detectable increase in the equilibrium actin monomer concentration determined by a radioassay. These results complement earlier observations indicating that cytochalasin B shortens actin filaments without net depolymerization. Analyzed in terms of Flory's classical network theory, this shortening accounts for the marked effect of cytochalasin B in dissolving the gel structure of F-actin crosslinked by actin-binding protein concentrations near the critical concentration for incipient gelation. Cytochalasin B decreased the annealing rate of low concentrations of actin filament fragments prepared by sonic disruption. The result is consistent with the idea that cytochalasin B binds to the ends of actin filaments, and may explain how cytochalasin B causes filament shortening.
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Phosphoglycerate mutase catalyzes the migration of a phosphoryl group from the C-3 position of 3-phosphoglycerate to the C-2 position. This glycolytic enzyme is a tetramer with four identical subunits.♥ \n\nCheck out this link for more:\nhttp://www.chem.uwec.edu/Modeling/GGProteinStructures/Pages/prs3b11.htm
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proto-oncogenes are genes that normally function in regulating proliferation. Mutations that activate them will usually cause the cell to growth without control (this is when we refer to them as oncogenes).\nTumor suppressor genes are caretakers and gatekeepers. They make sure to control uncontrolled proliferation and give the time to a cell to repair any damage. If necessary, wil cause the cell to die. If these genes get mutated then cells would tend to keep unrepaired DNA damages and turn into tumors.
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mRNA is capped with several guanosine residues before being exported from the nucleus. One way to detect mRNA capping is to use radioactive (radio-labeled) or fluorescent labeled guanosine. When the cell begins to add the G cap to the mRNA, it will incorporate the radiolabeled/fluorescent guanosine. After the cell has exported the mRNA into the cytoplasm, you can extract the mRNA and check to see where the labeled guanosine is.\n\nIf the theory of G-capping is true (which it is), then you should find that one end (the capped end) of the mRNA should be giving off a strong radioactive or fluorescent signal.\n\nYou can also sequence mRNA to find that there are several G residues on one end. These are just two methods...there are others.
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Entire courses and course of study are devoted to this question.  But here are some examples:\n\nSignal Transduction Pathways - This is a really broad category.  Cells communicate with the extracellular "milieu" using surface receptors.  When a certain signal molecule binds to the receptor, this initiates a signal cascade.  At the end of many of these cascades are transcription factors and regulatory pathways that can initiate or block transcription.  So the presence or absence of certain substances results in certain molecules that initiate transcription of certain genes.\n\nRhythms - Some proteins can interact with other proteins and regulate each others presence or absence.  This is particularly important for circadian rhythms and regulation of the cell cycle.  One protein initiates transcription of the another protein, and this other protein in turn down regulates transcription of the original protein.  The other protein eventually degrades, the the original protein's function returns.   \n\nIn essence, cells can sense what they need through proteins.  These proteins can signal other proteins which can eventually lead to the initiation or blocking of transcription. \n\nHope that helps!
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This is not a simple question.  Some hormones, once they activate the receptor are endocytosed with the receptor into the cell.  Therefore, these hormones can only activate the receptor one time.\n\nOther hormones activate receptors inside the cells (e.g. steroid hormones) and again, may stay attached to the receptor as it translocates to the nucleus to activate gene expression.\n\nLastly, still others may activate a surface receptor and then dissociate from the receptor, making them available to activate the receptor again.\n\nHope this was helpful.   If you go to Pubmed (enter "entrez pubmed" in your search engine), they have access to many online medical texts on cell biology.  You can search these books for their chapters and info. on hormones, receptors, etc.\n\nBest wishes.
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Reversible phosphorylation has long been an attractive mechanism to control cycles of coat assembly and disassembly during clathrin-mediated endocytosis. Many of the coat proteins are phosphorylated in vivo and in vitro. Our work has focused on the role of phosphorylation of the mu2 subunit of AP-2 (adaptor protein 2), which appears to be necessary for efficient cargo recruitment. Studies to probe the regulation of mu2 phosphorylation demonstrated that clathrin is a specific activator of the mu2 kinase, and, in permeabilized cells, cargo sequestration, driven by exogenously added clathrin, results in elevated levels of m2 phosphorylation. Furthermore, phosphorylated mu2 is mainly associated with assembled clathrin in vivo and its steady-state level is strongly reduced in cells depleted of clathrin heavy chain. Our results imply a central role for clathrin in the regulation of cargo selection via modulation of phospho-mu2 levels. This is therefore a novel regulatory role for clathrin that is independent of its structural role and that provides elegant spatial control of AP-2 and cargo interactions, ensuring that AP-2 is only activated at the correct cellular location and in the correct functional context. Ongoing studies are exploring further the roles of reversible phosphorylation in the coated vesicle cycle.
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A lot of things. But certain things include Chromosome integrity ( all of them present? in good shape?) and size. It is controlled by many enzymes known as cyclins.