Dicty News Electronic Edition Volume 17, number 8 October 13, 2001 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu. Back issues of Dicty-News, the Dicty Reference database and other useful information is available at DictyBase--http://dictybase.org. ======================== Dicty 2002 -- Italy ======================== Dear All, As anticipated at the Dicty 2001 meeting in La Jolla, I'm pleased to announce that the INTERNATIONAL DICTY CONFERENCE 2002 will take place in Italy from September 22 to September 27 at the Hotel Village Torre Normanna Altavilla Milicia (Palermo). A web page at www.unito.it, with a link to the Dicty server, will be activated in the near future. We hope that the international situation will clear up soon and that all of you will be able to come to the meeting. Salvo Bozzaro Enrico Bracco Adriano Ceccarelli ============== Abstracts ============== Expression patterns of 5'-Nucleotidase in Dictyostelium Muatasem Ubeidat, Can M. Eristi and Charles L. Rutherford* Biology Department, Molecular and Cellular Biology Section, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0406, USA Accepted Mechanisms of Development Abstract In order to analyze the expression pattern of 5'-nucleotidase (5nt) gene, we made fusion constructs in which the 5nt promoter directed the expression of b-galactosidase and green fluorescent protein (gfp). Reporter gene activity showed that the fusion genes were first expressed in the early aggregation stage. At the slug stage, 5nt was highly expressed in pstAB cells. As the slug moved along the substratum, high activity of b-galactosidase was detected in cells that were left behind in the slime sheath. At the early culmination stage, the 5nt-fusion gene was expressed at the interface of the prespore/prestalk regions. In the completed fruiting body, 5nt was expressed in the lower cup, in the slime sheath, and the basal disc. ----------------------------------------------------------------------------- Methanol and Acriflavine Resistance in Dictyostelium are Caused by Loss of Catalase Ma. Xenia U. Garcia1*, Catherine Roberts2*, Hannah Alexander1, A. Michael Stewart2, Adrian Harwood3, Stephen Alexander1 and Robert H. Insall2 Microbiology, in press Various chemicals with harmful effects are not themselves toxic, but are metabolized in vivo to produce toxic products. One example is methanol in Dictyostelium, which is lethal to cells containing the acrA gene, but relatively harmless to acrA mutants. This makes methanol resistance one of the tightest genetic selections in Dictyostelium. Loss of acrA also confers cross-resistance to unrelated compounds such as acriflavine and thiabendazole. We have used insertional mutagenesis to demonstrate that the acrA locus encodes the peroxisomal catalase A enzyme. Disruption of the catA gene results in parallel resistance to acriflavine. Molecular and biochemical studies of several previously characterized methanol resistant strains reveal that each lacks catalase activity. One allele, acrA2, contains a 13bp deletion which introduces a frameshift in the middle of the gene. The involvement of catalase in methanol resistance in Dictyostelium compares with its role in methanol metabolism in yeast and rodents. However, this is the first study to show that catalase is required for the toxicity of acriflavine. Our results imply that acriflavine and thiabendazole are precursors which must be oxidized to generate biologically active species. The catA/acrA gene is also a potentially invaluable negative selectable marker for Dictyostelium molecular genetics. ----------------------------------------------------------------------------- CRYSTAL STRUCTURE OF A DYNAMIN GTPASE DOMAIN IN BOTH NUCLEOTIDE-FREE AND GDP-BOUND FORMS Hartmut H. Niemann, Menno L. W. Knetsch, Anna Scherer, Dietmar J. Manstein & F. Jon Kull Department of Biophysics, Max-Planck-Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany EMBO J., in press. Dynamins form a family of multidomain GTPases involved in endocytosis, vesicle trafficking and maintenance of mitochondrial morphology. In contrast to the classical switch GTPases, a force generating function has been suggested for dynamins. Here we report the 2.3 crystal structure of the nucleotide-free and GDP-bound GTPase domain of Dictyostelium discoideum dynamin A. The GTPase domain is the most highly conserved region among dynamins. The globular structure contains the G-protein core fold, which is extended from a six-stranded b-sheet to an eight-stranded one by a 55 amino acid insertion. This topologically unique insertion distinguishes dynamins from other subfamilies of GTP-binding proteins. An additional N-terminal helix interacts with the C-terminal helix of the GTPase domain, forming a hydrophobic groove, which could be occupied by C-terminal parts of dynamin not present in our construct. The lack of major conformational changes between the nucleotide-free and the GDP-bound state indicate that mechano-chemical rearrangements in dynamin must occur during GTP-binding, GTP hydrolysis or phosphate release and are not linked to loss of GDP. ----------------------------------------------------------------------------- [End Dicty News, volume 17, number 8]