Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0162871 (abdominal aortic aneurysm)
 8,664 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The HslUV protease-chaperone complex degrades specific protein substrates in an ATP-dependent reaction. Current models propose that the HslU chaperone, a AAA protein of the Clp/Hsp100 family, binds and unfolds substrates and translocates the polypeptide into the catalytic cavity of the HslV protease. These processes are being characterized using substrates that are targeted to HslUV with a carboxy-terminal fusion of the natural substrate SulA or the carboxy-terminal 11 amino acid residues thereof. In a tandem fusion of green fluorescent protein with SulA, HslUV degrades the SulA moiety but not green fluorescent protein. Wild type and mutant Arc repressor variants are degraded; over a range of substrate stabilities, the specific rate of degradation and its dependence on substrate stability is similar to that of ClpXP. For a hyperstable Arc variant having an intermolecular disulfide bond, the rate of degradation by HslUV is an order of magnitude slower than by ClpXP. Similarity in degradation rates for a subset of substrates by HslUV and ClpXP suggests a similarity in mechanism of the apparent rate-limiting steps of unfolding and translocation by the chaperone components HslU and ClpX. The fall-off in degradation by HslUV for the more stable substrates that are degraded by ClpXP is consistent with the two systems acting on different spectra of biological substrates.
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PMID:Kinetics of protein substrate degradation by HslUV. 1503 45

The hypersensitive response (HR) is one of the most critical defense systems in higher plants. In order to understand its molecular basis, we have screened tobacco genes that are transcriptionally activated during the early stage of the HR by the differential display method. Among six genes initially identified, one was found encoding a 57 kDa polypeptide with 497 amino acids not showing significant similarity to any reported proteins except for the AAA domain (ATPase associated with various cellular activities) spanning over 230 amino acids. The bacterially expressed protein exhibited ATP hydrolysis activity, and a green fluorescent protein-fusion protein localized in the cytoplasm of onion epidermis cells. The protein was subsequently designated as NtAAA1 (Nicotiana tabacum AAA1). NtAAA1 transcripts were induced 6 h after HR onset not only by TMV but also by incompatible Psuedomonas syringae, indicating that NtAAA1 is under the control of the N-gene with a common role in pathogen responses. Expression of NtAAA1 was induced by jasmonic acid and ethylene, but not by salicylic acid (SA). It also occurred at a high level in SA-deficient tobacco plants upon TMV infection. When NtAAA1 was silenced by the RNAi method, accumulation of transcripts for PR-1a significantly increased during the HR. Treatments with SA induced higher expression of PR-1a and acidic PR-2 in RNAi transgenic plants than in wild-type counterparts. These results suggest that NtAAA1 mitigates the SA signaling pathway, and therefore that NtAAA1 modulates the pathogen response of the host plants by adjusting the HR to an appropriate level.
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PMID:A hypersensitive response-induced ATPase associated with various cellular activities (AAA) protein from tobacco plants. 1582 94

Hexameric ring-shaped ATPases of the AAA + (for ATPases associated with various cellular activities) superfamily power cellular processes in which macromolecular structures and complexes are dismantled or denatured, but the mechanisms used by these machine-like enzymes are poorly understood. By covalently linking active and inactive subunits of the ATPase ClpX to form hexamers, here we show that diverse geometric arrangements can support the enzymatic unfolding of protein substrates and translocation of the denatured polypeptide into the ClpP peptidase for degradation. These studies indicate that the ClpX power stroke is generated by ATP hydrolysis in a single subunit, rule out concerted and strict sequential ATP hydrolysis models, and provide evidence for a probabilistic sequence of nucleotide hydrolysis. This mechanism would allow any ClpX subunit in contact with a translocating polypeptide to hydrolyse ATP to drive substrate spooling into ClpP, and would prevent stalling if one subunit failed to bind or hydrolyse ATP. Energy-dependent machines with highly diverse quaternary architectures and molecular functions could operate by similar asymmetric mechanisms.
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PMID:Rebuilt AAA + motors reveal operating principles for ATP-fuelled machines. 1623 35

Clp/Hsp100 proteins comprise a large family of AAA(+) ATPases. Some Clp proteins function alone as molecular chaperones, whereas others act in conjunction with peptidases, forming ATP-dependent proteasome-like compartmentalized proteases. Protein degradation by Clp proteases is regulated primarily by substrate recognition by the Clp ATPase component. The ClpA and ClpX ATPases of Escherichia coli generally recognize short amino acid sequences that are located near the N or C terminus of a substrate. However, both ClpAP and ClpXP are able to degrade proteins in which the end containing the recognition signal is fused to GFP such that the signal is in the interior of the primary sequence of the substrate. Here, we tested whether the internal ClpA recognition signal was the sole element required for targeting the substrate to ClpA. The results show that, in the absence of a high-affinity peptide recognition signal at the terminus, two elements are important for recognition of GFP-RepA fusion proteins by ClpA. One element is the natural ClpA recognition signal located at the junction of GFP and RepA in the fusion protein. The second element is the C-terminal peptide of the fusion protein. Together, these two elements facilitate binding and unfolding by ClpA and degradation by ClpAP. The internal site appears to function similarly to Clp adaptor proteins but, in this case, is covalently attached to the polypeptide containing the terminal tag and both the "adaptor" and "substrate" modules are degraded.
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PMID:Two peptide sequences can function cooperatively to facilitate binding and unfolding by ClpA and degradation by ClpAP. 1641 Mar 55

Escherichia coli FtsH, which belongs to the AAA (ATPases associated with diverse cellular activities) family, is an ATP-dependent and membrane-bound protease. FtsH degrades misassembled membrane proteins and a subset of cytoplasmic regulatory proteins. It has been proposed that ATP-dependent proteases unfold substrate proteins and initiate a processive proteolysis from either terminus of the substrate polypeptide. We have found that FtsH degrades E. coli apo-flavodoxin (apo-Fld) but not holo-Fld containing non-covalently bound flavin mononucleotide (FMN). A mutant Fld carrying a substitution of Tyr94 to Asp (Fld(YD)) with a lower affinity for FMN was efficiently degraded by FtsH. To elucidate the directionality of Fld(YD) degradation by FtsH, we constructed several Fld(YD) fusion proteins with glutathione S-transferase (GST), green fluorescent protein (GFP), or both GST and GFP. It was found that FtsH was able to initiate degradation of the Fld(YD) moiety even when it was sandwiched by GST and GFP. Evidence indicated that FtsH can initiate proteolysis of GST-Fld(YD)-GFP from the Fld(YD) moiety by translocating an internal loop to the protease chamber in an ATP-dependent manner and that, at least, the proteolysis in the C to N direction proceeds processively.
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PMID:An AAA protease FtsH can initiate proteolysis from internal sites of a model substrate, apo-flavodoxin. 1648 14

The ATP-dependent integral membrane protease FtsH is universally conserved in bacteria. Orthologs exist in chloroplasts and mitochondria, where in humans the loss of a close FtsH-homolog causes a form of spastic paraplegia. FtsH plays a crucial role in quality control by degrading unneeded or damaged membrane proteins, but it also targets soluble signaling factors like sigma(32) and lambda-CII. We report here the crystal structure of a soluble FtsH construct that is functional in caseinolytic and ATPase assays. The molecular architecture of this hexameric molecule consists of two rings where the protease domains possess an all-helical fold and form a flat hexagon that is covered by a toroid built by the AAA domains. The active site of the protease classifies FtsH as an Asp-zincin, contrary to a previous report. The different symmetries of protease and AAA rings suggest a possible translocation mechanism of the target polypeptide chain into the interior of the molecule where the proteolytic sites are located.
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PMID:The molecular architecture of the metalloprotease FtsH. 1648 67

Photosynthetic organisms require chlorophyll and bacteriochlorophyll to harness light energy and to transform water and carbon dioxide into carbohydrates and oxygen. The biosynthesis of these pigments is initiated by magnesium chelatase, an enzyme composed of BchI, BchD, and BchH proteins, which catalyzes the insertion of Mg(2+) into protoporphyrin IX (Proto) to produce Mg-protoporphyrin IX. BchI and BchD form an ATP-dependent AAA(+) complex that transiently interacts with the Proto-binding BchH subunit, at which point Mg(2+) is chelated. In this study, controlled proteolysis, electron microscopy of negatively stained specimens, and single-particle three-dimensional reconstruction have been used to probe the structure and substrate-binding mechanism of the BchH subunit to a resolution of 25A(.) The apo structure contains three major lobe-shaped domains connected at a single point with additional densities at the tip of two lobes termed the "thumb" and "finger." With the independent reconstruction of a substrate-bound BchH complex (BchH.Proto), we observed a distinct conformational change in the thumb and finger subdomains. Prolonged proteolysis of native apo-BchH produced a stable C-terminal fragment of 45 kDa, and Proto was shown to protect the full-length polypeptide from degradation. Fitting of a truncated BchH polypeptide reconstruction identified the N- and C-terminal domains. Our results show that the N- and C-terminal domains play crucial roles in the substrate-binding mechanism.
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PMID:Substrate-binding model of the chlorophyll biosynthetic magnesium chelatase BchH subunit. 1826 81

Mutations of human spastin, an AAA (ATPases associated with diverse cellular activity) family protein, cause an autosomal dominant form of hereditary spastic paraplegia, which is characterized by weakness, spasticity and loss of the vibratory sense in the lower limbs. Recently, it has been reported that spastin displays microtubule-severing activity. We also previously reported that Caenorhabditis elegans spastin homologue SPAS-1 displays microtubule severing. However, the detailed molecular mechanism of microtubule severing remains unknown. Here, we describe that SPAS-1 forms a stable hexamer in a concentration-dependent manner and that ATPase activity of SPAS-1 is greatly stimulated by microtubules. Furthermore, MTBD (microtubule-binding domain) of SPAS-1 is essential for binding to microtubules. Taken these results together, we propose that MTBD of SPAS-1 plays a critical role in enrichment of SPAS-1 to microtubules, where SPAS-1 is concentrated and able to form a stable hexamer, subsequently its ATPase activity is stimulated. On the other hand, our mutational analyses revealed that the conserved aromatic and basic amino acid residues in the pore region are important for microtubule severing. We also detected the direct interaction of the extremely acidic C-terminal polypeptide of tubulin with SPAS-1. Consequently, we propose that the central pore residues are important for the recognition of substrates.
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PMID:Conserved aromatic and basic amino acid residues in the pore region of Caenorhabditis elegans spastin play critical roles in microtubule severing. 1961 44

The purpose of this study was to screen for genes involved in ovarian carcinogenesis in an attempt to develop an effective molecular-targeted therapy for ovarian cancer. We constructed retroviral expression libraries for the human ovarian cancer cell lines SHIN-3 and TYK-CPr, and performed a focus formation assay with 3T3 cells. As a result, proteasome subunit beta-type 2 (PSMB2), ubiquitin-specific protease 14 (USP14), and keratin 8 (KRT8) were identified from SHIN-3, and polymerase II RNA subunit (POLR2E), chaperonin containing T-complex polypeptide 1 subunit 4 (CCT4), glia maturation factor beta (GMFB), and neuroblastoma ras viral oncogene homolog (NRAS) from TYK-CPr. NRAS gene analysis revealed a CAA --> AAA substitution at codon 61, resulting in a Glu --> Lys change at position 61. When the mutant NRAS was introduced into fibroblasts for its expression, many transformed foci were generated, confirming the transforming ability of the mutant NRAS.
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PMID:Screening for genetic abnormalities involved in ovarian carcinogenesis using retroviral expression libraries. 1978 49

Switches between different phenotypes and their underlying states of gene transcription occur as cells respond to intrinsic developmental cues or adapt to changing environmental conditions. Post-translational modification of the master regulatory transcription factors that define the initial phenotype is a common strategy to direct such transitions. Emerging evidence indicates that the modification of key transcription factors by the small polypeptide ubiquitin has a central role in many of these transitions. However, the molecular mechanisms by which ubiquitylation regulates the switching of promoters between active and inactive states are largely unknown. Ubiquitylation of the yeast transcriptional repressor alpha2 is necessary to evoke the transition between mating-types, and here we dissect the impact of this modification on alpha2 dynamics at its target promoters. Ubiquitylation of alpha2 does not alter DNA occupancy by depleting the existing pool of the transcription factor, despite its well-characterized function in directing repressor turnover. Rather, alpha2 ubiquitylation has a direct role in the rapid removal of the repressor from its DNA targets. This disassembly of alpha2 from DNA depends on the ubiquitin-selective AAA-ATPase Cdc48. Our findings expand the functional targets of Cdc48 to include active transcriptional regulatory complexes in the nucleus. These data reveal an ubiquitin-dependent extraction pathway for dismantling transcription factor-DNA complexes and provide an archetype for the regulation of transcriptional switching events by ubiquitylation.
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PMID:A ubiquitin-selective AAA-ATPase mediates transcriptional switching by remodelling a repressor-promoter DNA complex. 1991 56


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