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dictyNews Volume 17 Number 08
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.
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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.
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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.
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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.
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[End Dicty News, volume 17, number 8]
