Publications (9) View all
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Article: Structure and activity of the only human RNase T2.
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ABSTRACT: Mutations in the gene of human RNase T2 are associated with white matter disease of the human brain. Although brain abnormalities (bilateral temporal lobe cysts and multifocal white matter lesions) and clinical symptoms (psychomotor impairments, spasticity and epilepsy) are well characterized, the pathomechanism of RNase T2 deficiency remains unclear. RNase T2 is the only member of the Rh/T2/S family of acidic hydrolases in humans. In recent years, new functions such as tumor suppressing properties of RNase T2 have been reported that are independent of its catalytic activity. We determined the X-ray structure of human RNase T2 at 1.6 Å resolution. The α+β core fold shows high similarity to those of known T2 RNase structures from plants, while, in contrast, the external loop regions show distinct structural differences. The catalytic features of RNase T2 in presence of bivalent cations were analyzed and the structural consequences of known clinical mutations were investigated. Our data provide further insight into the function of human RNase T2 and may prove useful in understanding its mode of action independent of its enzymatic activity.Nucleic Acids Research 06/2012; 40(17):8733-42. · 8.03 Impact Factor -
Article: Function of Ech hydrogenase in ferredoxin-dependent, membrane-bound electron transport in Methanosarcina mazei.
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ABSTRACT: Reduced ferredoxin is an intermediate in the methylotrophic and aceticlastic pathway of methanogenesis and donates electrons to membrane-integral proteins, which transfer electrons to the heterodisulfide reductase. A ferredoxin interaction has been observed previously for the Ech hydrogenase. Here we present a detailed analysis of a Methanosarcina mazei Delta ech mutant which shows decreased ferredoxin-dependent membrane-bound electron transport activity, a lower growth rate, and faster substrate consumption. Evidence is presented that a second protein whose identity is unknown oxidizes reduced ferredoxin, indicating an involvement in methanogenesis from methylated C(1) compounds.Journal of bacteriology 11/2009; 192(3):674-8. · 3.94 Impact Factor -
Article: Molecular characterization of folate receptor 1 mutations delineates cerebral folate transport deficiency.
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ABSTRACT: Cerebral folate transport deficiency is an inherited brain-specific folate transport defect that is caused by mutations in the folate receptor 1 gene coding for folate receptor alpha (FRα). This genetic defect gives rise to a progressive neurological disorder with late infantile onset. We screened 72 children with low 5-methyltetrahydrofolate concentrations in the cerebrospinal fluid and neurological symptoms that developed after infancy. We identified nucleotide alterations in the folate receptor 1 gene in 10 individuals who shared developmental regression, ataxia, profound cerebral hypomyelination and cerebellar atrophy. We found four novel pathogenic alleles, one splice mutation and three missense mutations. Heterologous expression of the missense mutations, including previously described mutants, revealed minor decrease in protein expression but loss of cell surface localization, mistargeting to intracellular compartments and thus absence of cellular binding of folic acid. These results explain the functional loss of folate receptor alpha for all detected folate receptor 1 mutations. Three individuals presenting a milder clinical phenotype revealed very similar biochemical and brain imaging data but partially shared pathogenic alleles with more severely affected patients. Thus, our studies suggest that different clinical severities do not necessarily correlate with residual function of folate receptor alpha mutants and indicate that additional factors contribute to the clinical phenotype in cerebral folate transport deficiency.Brain 05/2012; 135(Pt 7):2022-31. · 9.46 Impact Factor -
Article: Folate receptor alpha defect causes cerebral folate transport deficiency: a treatable neurodegenerative disorder associated with disturbed myelin metabolism.
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ABSTRACT: Sufficient folate supplementation is essential for a multitude of biological processes and diverse organ systems. At least five distinct inherited disorders of folate transport and metabolism are presently known, all of which cause systemic folate deficiency. We identified an inherited brain-specific folate transport defect that is caused by mutations in the folate receptor 1 (FOLR1) gene coding for folate receptor alpha (FRalpha). Three patients carrying FOLR1 mutations developed progressive movement disturbance, psychomotor decline, and epilepsy and showed severely reduced folate concentrations in the cerebrospinal fluid (CSF). Brain magnetic resonance imaging (MRI) demonstrated profound hypomyelination, and MR-based in vivo metabolite analysis indicated a combined depletion of white-matter choline and inositol. Retroviral transfection of patient cells with either FRalpha or FRbeta could rescue folate binding. Furthermore, CSF folate concentrations, as well as glial choline and inositol depletion, were restored by folinic acid therapy and preceded clinical improvements. Our studies not only characterize a previously unknown and treatable disorder of early childhood, but also provide new insights into the folate metabolic pathways involved in postnatal myelination and brain development.The American Journal of Human Genetics 10/2009; 85(3):354-63. · 10.60 Impact Factor -
Article: The homeodomain of PAX6 is essential for PAX6-dependent activation of the rat glucagon gene promoter: evidence for a PH0-like binding that induces an active conformation.
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ABSTRACT: The transcription factor PAX6 plays an important role in transcriptional regulation of the peptide hormone glucagon from pancreatic alpha-cells. PAX6 contains two DNA binding domains, the paired domain (PD) and the homeodomain (HD). While the interaction of the PD with the PAX6 responsive elements G1 and G3 in the rat glucagon gene promoter is well understood, the role of the PAX6 HD for PAX6 binding and function on G1 and G3 remains unclear. In EMSA studies the PAX6 HD was found to be mandatory for PAX6 binding to G1 but not to G3. Transient transfections with luciferase reporter gene constructs revealed the HD to be critical for proper function of PAX6 on both, G1 and G3. Transfection data with variant promoter constructs and limited proteolysis assays demonstrated that the DNA sequence located 5' to the PD binding site plays an important role for PAX6 function and its conformation on the elements G1 and G3. Taken together, our data indicate a PH0-like binding of PAX6 to the glucagon promoter elements G1 and G3 where the HD binding site is abutted directly to the PD binding motif. The data suggest that the PH0-like binding induces a transcriptionally active conformation of PAX6.Biochimica et Biophysica Acta 03/2009; 1789(5):403-12. · 4.66 Impact Factor
