Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q86TM3 (cage)
 29,987 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

MutLalpha, a heterodimer of MLH1 and PMS2, plays a central role in human DNA mismatch repair. It interacts ATP-dependently with the mismatch detector MutSalpha and assembles and controls further repair enzymes. We tested if the interaction of MutLalpha with DNA-bound MutSalpha is impaired by cancer-associated mutations in MLH1, and identified one mutation (Ala128Pro) which abolished interaction as well as mismatch repair activity. Further examinations revealed three more residues whose mutation interfered with interaction. Homology modelling of MLH1 showed that all residues clustered in a small accessible surface patch, suggesting that the major interaction interface of MutLalpha for MutSalpha is located on the edge of an extensive beta-sheet that backs the MLH1 ATP binding pocket. Bioinformatic analysis confirmed that this patch corresponds to a conserved potential protein-protein interaction interface which is present in both human MLH1 and its E.coli homologue MutL. MutL could be site-specifically crosslinked to MutS from this patch, confirming that the bacterial MutL-MutS complex is established by the corresponding interface in MutL. This is the first study that identifies the conserved major MutLalpha-MutSalpha interaction interface in MLH1 and demonstrates that mutations in this interface can affect interaction and mismatch repair, and thereby can also contribute to cancer development.
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PMID:Mutations in the MutSalpha interaction interface of MLH1 can abolish DNA mismatch repair. 1713 87

RecQ helicases are essential for the maintenance of chromosome stability. In addition to DNA unwinding, some RecQ enzymes have an intrinsic DNA strand annealing activity. The function of this dual enzymatic activity and the mechanism that regulates it is, however, unknown. Here, we describe two quaternary forms of the human RECQ1 helicase, higher-order oligomers consistent with pentamers or hexamers, and smaller oligomers consistent with monomers or dimers. Size exclusion chromatography and transmission electron microscopy show that the equilibrium between the two assembly states is affected by single-stranded DNA (ssDNA) and ATP binding, where ATP or ATPgammaS favors the smaller oligomeric form. Our three-dimensional electron microscopy reconstructions of human RECQ1 reveal a complex cage-like structure of approximately 120 A x 130 A with a central pore. This oligomeric structure is stabilized under conditions in which RECQ1 is proficient in strand annealing. In contrast, competition experiments with the ATPase-deficient K119R and E220Q mutants indicate that RECQ1 monomers, or tight binding dimers, are required for DNA unwinding. Collectively, our findings suggest that higher-order oligomers are associated with DNA strand annealing, and lower-order oligomers with DNA unwinding.
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PMID:Different quaternary structures of human RECQ1 are associated with its dual enzymatic activity. 1722 44

Autoantibodies against alpha-enolase, a glycolytic enzyme, have been frequently associated with visual loss and retinal degeneration in patients with autoimmune and cancer-associated retinopathy; however their role in the pathogenicity of retinopathy has not been fully explained. Thus, we examined the causative role of anti-enolase antibodies on retinal cells. In the in vitro studies reported here, we found that Enol-1 monoclonal antibody against alpha-enolase significantly inhibited the catalytic function of enolase, which resulted in the depletion of glycolytic ATP. Enol-1 significantly increased intracellular Ca(2+), which led to Bax translocation to the mitochondria, and the release of cytochrome c into the cytoplasm--events that correlated with the initiation of apoptosis. Normal IgG did not induce intracellular calcium or reduce cytosolic ATP. L-type voltage-gated calcium channel blockers (nifedipine, D-cis-diltiazem, and verapamil) were effective in blocking the Ab-induced intracellular Ca(2+) rise and induction of Bax. Based on these findings we propose that chronic access of autoantibodies to the retina results in the inhibition of enolase catalytic function, depletion of ATP, and elevation in intracellular Ca(2+), leading to deregulation of glycolysis in retinal neurons and their destruction.
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PMID:The role of anti-alpha-enolase autoantibodies in pathogenicity of autoimmune-mediated retinopathy. 1723 87

Double chromodomains occur in CHD proteins, which are ATP-dependent chromatin remodeling factors implicated in RNA polymerase II transcription regulation. Biochemical studies suggest important differences in the histone H3 tail binding of different CHD chromodomains. In human and Drosophila, CHD1 double chromodomains bind lysine 4-methylated histone H3 tail, which is a hallmark of transcriptionally active chromatin in all eukaryotes. Here, we present the crystal structure of the yeast CHD1 double chromodomains, and pinpoint their differences with that of the human CHD1 double chromodomains. The most conserved residues in these double chromodomains are the two chromoboxes that orient adjacently. Only a subset of CHD chromoboxes can form an aromatic cage for methyllysine binding, and methyllysine binding requires correctly oriented inserts. These factors preclude yeast CHD1 double chromodomains from interacting with the histone H3 tail. Despite great sequence similarity between the human CHD1 and CHD2 chromodomains, variation within an insert likely prevents CHD2 double chromodomains from binding lysine 4-methylated histone H3 tail as efficiently as in CHD1. By using the available structural and biochemical data we highlight the evolutionary specialization of CHD double chromodomains, and provide insights about their targeting capacities.
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PMID:Molecular implications of evolutionary differences in CHD double chromodomains. 1743 64

We report directional memory of spontaneous nanoscale displacements of an individual bead firmly anchored to the cytoskeleton of a living cell. A novel method of analysis shows that for shorter time intervals cytoskeletal displacements are antipersistent and thus provides direct evidence in a living cell of molecular trapping and caged dynamics. At longer time intervals displacements are persistent. The transition from antipersistence to persistence is indicative of a time-scale for cage rearrangements and is found to depend upon energy release due to ATP hydrolysis and proximity to a glass transition. Anomalous diffusion is known to imply memory, but we show here that memory is attributed to direction rather than step size. As such, these data are the first to provide a molecular-scale physical picture describing the cytoskeletal remodelling process and its rate of progression.
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PMID:Directional memory and caged dynamics in cytoskeletal remodelling. 1763 Dec 76

Cytoskeletal (CSK) dynamics such as remodeling and reorganization can be studied by tracking the spontaneous motion of CSK-bound particles. Particle motion is thought to be driven by local, ATP-dependent intracellular force fluctuations due to polymerization processes and motor proteins, and to be impeded by a viscoelastic, metastable cytoskeletal network. The mechanisms that link particle motion to force fluctuations and the CSK dynamics remain unclear. We report simultaneous measurements of the spontaneous motion of CSK-bound particles and of cellular force fluctuations. Cellular force fluctuations were measured by tracking fluorescent markers embedded in an elastic polyacrylamide hydrogel substrate that served as an extracellular matrix (ECM). The motion of CSK-bound particles and markers embedded in the ECM showed both persistence and superdiffusive behavior. Moreover, the movements of CSK-bound beads were temporally and spatially correlated with force fluctuations in the ECM. The findings suggest that the spontaneous motion of CSK-bound beads is driven not by random, local stress fluctuations within a viscoelastic continuum or cage, but rather by stress fluctuations within a tensed and constantly remodeling CSK network that transmits stresses over considerable distances to the ECM.
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PMID:Stress fluctuations and motion of cytoskeletal-bound markers. 1767 5

The GroEL chaperonin has the ability to behave as an unfoldase, repeatedly denaturing proteins upon binding, which in turn can free them from kinetic traps and increase their folding rates. The complex formed by GroEL+GroES+ATP can also act as an infinite dilution cage, enclosing proteins within a protective container where they can fold without danger of aggregation. Controversy remains over which of these two properties is more critical to the GroEL/ES chaperonin's function. We probe the importance of the unfoldase nature of GroEL under conditions where aggregation is the predominant protein degradation pathway. We consider the effect of a hypothetical mutation to GroEL which increases the cycle frequency of GroEL/ES by increasing the rate of hydrolysis of GroEL-bound ATP. Using a simple kinetic model, we show that this modified chaperonin would be self-defeating: any potential reduction in folding time would be negated by an increase in time spent in the bulk, causing an increase in aggregation and a net decrease in protein folding yields.
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PMID:Do chaperonins boost protein yields by accelerating folding or preventing aggregation? 1819 77

Multiple cellular stressors, including activation of the tumour suppressor p53, can stimulate autophagy. Here we show that deletion, depletion or inhibition of p53 can induce autophagy in human, mouse and nematode cells subjected to knockout, knockdown or pharmacological inhibition of p53. Enhanced autophagy improved the survival of p53-deficient cancer cells under conditions of hypoxia and nutrient depletion, allowing them to maintain high ATP levels. Inhibition of p53 led to autophagy in enucleated cells, and cytoplasmic, not nuclear, p53 was able to repress the enhanced autophagy of p53(-/-) cells. Many different inducers of autophagy (for example, starvation, rapamycin and toxins affecting the endoplasmic reticulum) stimulated proteasome-mediated degradation of p53 through a pathway relying on the E3 ubiquitin ligase HDM2. Inhibition of p53 degradation prevented the activation of autophagy in several cell lines, in response to several distinct stimuli. These results provide evidence of a key signalling pathway that links autophagy to the cancer-associated dysregulation of p53.
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PMID:Regulation of autophagy by cytoplasmic p53. 1845 41

We investigated the presence of EP1 receptor in the urothelium and its role in micturition reflex by examining the effect of intravesical administration of prostaglandin E(2) (PGE2), an EP1 agonist (ONO-DI-004), acetic acid, and capsaicin. Age-matched EP1-KO mice and C57BL/6 wild-type (WT) mice were used. Western blots and standard immunohistochemical procedures were performed. Cystometrygram (CMG) was performed without anesthesia in a restraining cage. ATP release from the cultured urothelium cells was performed using luciferin-luciferase luminometry. The EP1 receptor was found to be present in the urothelium. In WT mice, PGE2 infusion shortened the intercontraction interval (ICI) in a dose-dependent fashion; however, it did not alter the ICI in EP1-KO mice. The EP1 agonist significantly shortened the ICI in WT mice, but not in EP1-KO mice. Acetic acid and capsaicin shortened the ICI in both WT mice and EP1-KO mice. EP1 agonist, PGE2 and capsaicin provoked ATP release from cultured urothelial cells. These results suggest that EP1 receptor was present in bladder urothelium, and could be activated by PGE2 to release ATP. EP1 receptor in urothelium might be important for reflex voiding in pathological conditions.
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PMID:Urothelium EP1 receptor facilitates the micturition reflex in mice. 1848 May 52

Due to its unmatched resolution, gel electrophoresis is an indispensable tool for the analysis of diverse biomolecules. By adaptation of the electrophoretic conditions, even fragile protein complexes as parts of intracellular networks migrate through the gel matrix under sustainment of their integrity. If the thickness of such native gels is significantly increased compared to the analytical version, also high sample loads can be processed. However, the cage-like network obstructs an in-depth analysis for deciphering structure and function of protein complexes and other species. Consequently, the biomolecules have to be removed from the gel matrix into solution. Several approaches summarized in this review tackle this problem. While passive elution relies on diffusion processes, electroelution employs an electric field to force biomolecules out of the gel. An alternative procedure requires a special electrophoresis setup, the continuous elution device. In this apparatus, molecules migrate in the electric field until they leave the gel and were collected in a buffer stream. Successful isolation of diverse protein complexes like photosystems, ATP-dependent enzymes or active respiratory supercomplexes and some other bioparticles demonstrates the versatility of preparative electrophoresis. After liberating particles out of the gel cage, numerous applications are feasible. They include elucidation of the individual components up to high resolution structures of protein complexes. Therefore, preparative electrophoresis can complement standard purification methods and is in some cases superior to them.
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PMID:Preparative isolation of protein complexes and other bioparticles by elution from polyacrylamide gels. 1849 38


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