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Structural Implications (structural + implication)
Selected AbstractsStructural implications of a G170R mutation of alanine:glyoxylate aminotransferase that is associated with peroxisome-to-mitochondrion mistargetingACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2010Snezana Djordjevic In a subset of patients with the hereditary kidney-stone disease primary hyperoxaluria type 1 (PH1), the liver-specific enzyme alanine:glyoxylate aminotransferase (AGT) is mistargeted from peroxisomes to mitochondria. This is a consequence of the combined presence of the common P11L polymorphism and a disease-specific G170R mutation. In this paper, the crystal structure of mutant human AGT containing the G170R replacement determined at a resolution of 2.6,Å is reported. The crystal structure of AGT consists of an intimate dimer in which an extended N-terminal segment of 21 amino acids from one subunit wraps as an elongated irregular coil around the outside of the crystallographic symmetry-related subunit. In addition to the N-terminal segment, the monomer structure contains a large domain of 261 amino acids and a small C-terminal domain of 110 amino acids. Comparison of the mutant AGT structure and that of wild-type normal AGT shows that the two structures are almost identical, with a backbone-atom r.m.s. deviation of 0.34,Å. However, evidence of significant local structural changes in the vicinity of the G170R mutation might be linked to the apparent decrease in protein stability. [source] Transitions of serum albumin in patients with glomerulosclerosis ,in vivo' characterization by electrophoretic titration curvesELECTROPHORESIS, Issue 14 2006Maurizio Bruschi Abstract HSA functions as a physiological transporter of solutes and small molecules that induce structural transitions ,in vitro'. Analysis of these transitions requires prior purification of HSA that could introduce bias due to conformational changes. We utilized electrophoretic titration curves to describe a neutral to acid (N,A) transition of HSA directly in sera of seven patients with active focal segmental glomerulosclerosis (FSGS). The divergent electrophoretic profile of HSA was characterized by a shift in the range of pHs between 4.5 and 7.5 with an average variation of free electrophoretic mobility corresponding to loss of 1 positive charge in the pKa protonation range of histidyl residues and should involve domain I of HSA. ,In-gel' determination by maleimide-PEO2-biotin of free SH 34 of domain I showed inaccessibility of the dye at this site in pathological HSA and alkylation with the same complex induced N,A transition in normal HSA. Potential binders of free imidazoles such as Ca++ and/or of SH 34 such as NO were excluded on the basis of direct titration and studies on binding stimulation. This is the first report describing a transition of HSA directly ,in vivo', and the utilization of electrophoretic titration curves was critical to this purpose. This transition appears to be specific to FSGS and is unrelated to the nephrotic syndrome, Ca++ and NO binding. Spectroscopic analysis will elucidate the structural implication. [source] Mutation analysis in mitochondrial fatty acid oxidation defects: Exemplified by acyl-CoA dehydrogenase deficiencies, with special focus on genotype,phenotype relationshipHUMAN MUTATION, Issue 3 2001Niels Gregersen Abstract Mutation analysis of metabolic disorders, such as the fatty acid oxidation defects, offers an additional, and often superior, tool for specific diagnosis compared to traditional enzymatic assays. With the advancement of the structural part of the Human Genome Project and the creation of mutation databases, procedures for convenient and reliable genetic analyses are being developed. The most straightforward application of mutation analysis is to specific diagnoses in suspected patients, particularly in the context of family studies and for prenatal/preimplantation analysis. In addition, from these practical uses emerges the possibility to study genotype,phenotype relationships and investigate the molecular pathogenesis resulting from specific mutations or groups of mutations. In the present review we summarize current knowledge regarding genotype,phenotype relationships in three disorders of mitochondrial fatty acid oxidation: very-long chain acyl-CoA dehydrogenase (VLCAD, also ACADVL), medium-chain acyl-CoA dehydrogenase (MCAD, also ACADM), and short-chain acyl-CoA dehydrogenase (SCAD, also ACADS) deficiencies. On the basis of this knowledge we discuss current understanding of the structural implications of mutation type, as well as the modulating effect of the mitochondrial protein quality control systems, composed of molecular chaperones and intracellular proteases. We propose that the unraveling of the genetic and cellular determinants of the modulating effects of protein quality control systems may help to assess the balance between genetic and environmental factors in the clinical expression of a given mutation. The realization that the effect of the monogene, such as disease-causing mutations in the VLCAD, MCAD, and SCAD genes, may be modified by variations in other genes presages the need for profile analyses of additional genetic variations. The rapid development of mutation detection systems, such as the chip technologies, makes such profile analyses feasible. However, it remains to be seen to what extent mutation analysis will be used for diagnosis of fatty acid oxidation defects and other metabolic disorders. Hum Mutat 18:169,189, 2001. © 2001 Wiley-Liss, Inc. [source] Mechanical implications of estrogen supplementation in early postmenopausal womenJOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2010Felix W Wehrli Abstract Whereas the structural implications of drug intervention are well established, there are few data on the possible mechanical consequences of treatment. In this work we examined the changes in elastic and shear moduli (EM and SM) in a region of trabecular bone in the distal radius and distal tibia of early postmenopausal women on the basis of MRI-based micro-finite-element (µFE) analysis. Whole-section axial stiffness (AS) encompassing both trabecular and cortical compartments was evaluated as well. The study was conducted on previously acquired high-resolution images at the two anatomic sites. Images were processed to yield a 3D voxel array of bone-volume fraction (BVF), which was converted to a µFE model of hexahedral elements in which tissue modulus was set proportional to voxel BVF. The study comprised 65 early postmenopausal women (age range 45 to 55 years), of whom 32 had chosen estrogen supplementation (estradiol group); the remainder had not (control group). Subjects had been scanned at baseline and 12 and 24 months thereafter. At the distal tibia, EM and SM were reduced by 2.9% to 5.5% in the control group (p,<,.05 to <.005), but there was no change in the estradiol subjects. AS decreased 3.9% (4.0%) in controls (p,<,.005) and increased by 5.8% (6.2%) in estradiol group subjects (p,<,.05) at 12 (24) months. At the distal radius, EM and SM changes from baseline were not significant, but at both time points AS was increased in estradiol group subjects and decreased in controls (p,<,.005 to <.05), albeit by a smaller margin than at the tibia. EM and SM were strongly correlated with BV/TV (r2,=,0.44 to 0.92) as well as with topologic parameters expressing the ratio of plates to rods (r2,=,0.45 to 0.82), jointly explaining up to 96% of the variation in the mechanical parameters. Finally, baseline AS was strongly correlated between the two anatomic sites (r2,=,0.58), suggesting that intersubject variations in the bone's mechanical competence follows similar mechanisms. In conclusion, the results demonstrate that micro-MRI-based µFE models are suited for the study of the mechanical implications of antiresorptive treatment. The data further highlight the anabolic effect of short-term estrogen supplementation. © 2010 American Society for Bone and Mineral Research [source] | ||||||||||