CSM News
Electronic Edition
Volume 5, number 2
July 8, 1995

Please submit abstracts of your papers as soon as they have been
accepted for publication by sending them to CSM-News@worms.cmsbio.nwu.edu.

Back issues of CSM-News, the CSM Reference database and other useful
information is available by anonymous ftp from worms.cmsbio.nwu.edu
[165.124.233.50], via Gopher at the same address, or by World Wide Web
at the URL "http://worms.cmsbio.nwu.edu/dicty.html"

===========
 Abstracts
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Sally K.A. Woodward, Michael A. Geeves and Dietmar J. Manstein

KINETIC CHARACTERISATION OF THE CATALYTIC DOMAIN OF DICTYOSTELIUM DISCOIDEUM
MYOSIN

Biochemistry, in press
 
   The myosin head consists of a globular motor or catalytic domain
that contains both the catalytic and actin binding sites, and a neck
region which consists of a 8.5 nm a-helix that emerges from the
globular part of the heavy chain and is stabilised by the binding of
the essential and regulatory light chains. High levels of M754, a
recombinant polyhistidine-tagged catalytic domain-like fragment of
myosin II, were produced in D. discoideum and purified using a rapid
extraction protocol and metal chelate chromatography. Approximately
1.2 mg of homogenous, functional protein was obtained per g of cells.
Kinetic analysis of M754 showed that the recombinant protein still has
all the typical properties of a myosin ATPase. However, the removal of
the light chain domain does have a pronounced effect on enzymatic
activity. Nucleotide on-rates are 7- to 16-fold slower for M754 than
for a myosin head fragment that includes the neck region. In contrast,
the rate of ATP binding and dissociating the actin bound catalytic
domain is ten-fold increased. Overall the results indicate that the
truncation of the heavy chain affects the nucleotide binding site and
the communication between the nucleotide and actin binding
sites. Furthermore, it seems that the nucleotide site of M754 is not
fully formed but binding to actin or ATP stabilises the structure in
general and the nucleotide binding site in particular.

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RNA POLYMERASE II TRANSCRIBES Dictyostelium UNTRANSLATABLE 
GENE, dutA, SPECIFICALLY IN THE DEVELOPMENTAL PHASE

Hiroshi KUMIMOTO, Hiderou YOSHIDA and Koji OKAMOTO

Department of Botany, Faculty of Science, Kyoto University, 
Kyoto 606-01, Japan

BBRC, in press

SUMMARY

   In Dictyostelium discoideum, a novel type of RNA (dutA RNA), which
is untranslatable, cytosolic and 1.3 kb in size, appears specifically
after the aggregation stage [Yoshida, H. et al. (1994) Nucleic Acids
Res. 22, 41-46].  We here show that the dutA gene is transcribed by
RNA polymerase II, based on its a-amanitin sensitive nature of in
vitro transcriptional activity. We also show that the stage-specific
accumulation of dutA RNA is primarily due to the stage-specific
enhancement of the transcriptional activity of the gene.

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[End CSM News, volume 5, number 11]