dictyNews
Electronic Edition
Volume 29, number 17
December 21, 2007

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Abstracts
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Mechanism, Regulation, and Functional Properties of Dictyostelium 
Myosin-1B.

Georgios Tsiavaliaris(1), Setsuko Fujita-Becker(2), Ulrike Duerrwang(2), 
Ralph P. Diensthuber(1), Michael A. Geeves(3),   and Dietmar J. Manstein(1,2)

(1)Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 
Carl-Neuberg-Straße 1, D-30623 Hannover, Germany; 
(2)Department of Biophysics, Max-Planck-Institute for Medical Research, 
Jahnstr. 29, D-69120 Heidelberg, Germany; 
(3)Department of Biosciences, University of Kent, Canterbury CT2 7NJ, 
United Kingdom.

Corresponding author: gtsiaval@bpc.mh-hannover.de


JBC, in press

Myosin-1B is one of three long-tailed class-1 myosins containing an 
ATP-insensitive actin-binding site in the tail region that are produced 
in Dictyostelium discoideum. Myosin-1B localizes to actin-rich structures 
at the leading edge of migrating cells, where it has been implicated in 
the formation and retraction of membrane projections, the recycling of 
plasma membrane components, and intracellular particle transport. Here, 
we use a combination of molecular engineering approaches to describe the 
kinetic and motile properties of the myosin-1B motor and its regulation 
by TEDS-site phosphorylation. Our results show that myosin-1B is a low 
duty ratio motor and displays the fastest nucleotide binding kinetics 
of any of the Dictyostelium class-1 myosins studied, so far. Different 
from Dictyostelium myosin-1D and myosin-1E, dephosphorylated myosin-1B 
is not inactivated but moves actin filaments efficiently, albeit at an 
up to 8-fold slower velocity in the in vitro motility assay. A further 
difference is that myosin-1B lacks the ability to switch between rapid 
movement and bearing tension upon physiological changes of free 
Mg2+-ions. In this respect, its motor properties appear to be more 
closely related to Dictyostelium myosin-2 and rabbit skeletal muscle 
myosin.


Submitted by: Georgios Tsiavaliaris [gtsiaval@bpc.mh-hannover.de]
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[End dictyNews, volume 29, number 17]