David Hummel

Publications (2)19.36 Total impact

• Article: Synteny perturbations between wheat homoeologous chromosomes caused by locus duplications and deletions correlate with recombination rates.

  Eduard D Akhunov, Alina R Akhunova, Anna M Linkiewicz, Jorge Dubcovsky, David Hummel, Gerry Lazo, Shiaoman Chao, Olin D Anderson, Jacques David, Lili Qi, [......], Junhua Peng, Nora L V Lapitan, Emily J Wennerlind, Vivienne Nduati, James A Anderson, Deepak Sidhu, Kulvinder S Gill, Patrick E McGuire, Calvin O Qualset, Jan Dvorak
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  ABSTRACT: Loci detected by Southern blot hybridization of 3,977 expressed sequence tag unigenes were mapped into 159 chromosome bins delineated by breakpoints of a series of overlapping deletions. These data were used to assess synteny levels along homoeologous chromosomes of the wheat A, B, and D genomes, in relation to both bin position on the centromere-telomere axis and the gradient of recombination rates along chromosome arms. Synteny level decreased with the distance of a chromosome region from the centromere. It also decreased with an increase in recombination rates along the average chromosome arm. There were twice as many unique loci in the B genome than in the A and D genomes, and synteny levels between the B genome chromosomes and the A and D genome homoeologues were lower than those between the A and D genome homoeologues. These differences among the wheat genomes were attributed to differences in the mating systems of wheat diploid ancestors. Synteny perturbations were characterized in 31 paralogous sets of loci with perturbed synteny. Both insertions and deletions of loci were detected and both preferentially occurred in high recombination regions of chromosomes.
  Proceedings of the National Academy of Sciences 10/2003; 100(19):10836-41. · 9.68 Impact Factor
• Source

  Available from: John C Voss

  Article: Overexpression, purification, and site-directed spin labeling of the Nramp metal transporter from Mycobacterium leprae.

  Ian Reeve, David Hummel, Nathan Nelson, John Voss, David Hummell
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  ABSTRACT: It has long been recognized that the pathogenicity of a broad range of intracellular parasites depends on the availability of transition metal ions, especially iron. Nramp1 (natural resistance-associated macrophage protein 1), a proton-coupled divalent metal ion transporter, has been identified as a controlling factor in the resistance or susceptibility to infection with a diverse range of intracellular pathogens such as Toxoplasma, Salmonella, Mycobacterium, and Leishmania. The role of divalent metal ion transport is even more compelling given the existence of Nramp homologs in several intracellular parasites, such as mycobacteria. We have confirmed the functional homology of the Nramp homologue from Mycobacterium leprae by using a yeast complementation assay for divalent cation uptake. To facilitate a concerted biochemical and structural analysis of this important class of transporters, the M. leprae Nramp was expressed in Escherichia coli. Dual affinity tags were engineered at the N and C termini to allow for isolation of full-length protein at >95% purity. Site-directed spin labeling of Cys-299 reveals a flexible hinge-like domain. A weak dipolar interaction is detected between the nitroxide and paramagnetic transition ions, indicating this position is approximately 19 A from the nearest high affinity binding site.
  Proceedings of the National Academy of Sciences 06/2002; 99(13):8608-13. · 9.68 Impact Factor