76 / 79
Engineering Approaches to Biomolecular Motors: From in vitro to in vivo Poster Abstracts
71
28-POS
Board 28
Increased Diffusion of Enzymes Catalyzing Exothermic Reactions
Konstantinos Tsekouras
, Steve Presse.
Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA.
We recently demonstrated (Riedel et al. Nature 2015) that enzymes catalyzing exothermic
reactions exhibit increased diffusion in the presence of their substrate, confirming experiments
done by the group of A. Sen. We concluded that the energy released by the turnover event briefly
accelerates the enzyme's center of mass resulting in a short ballistic motion of the enzyme; this
transient increase registers as an observed diffusion coefficient rise. Although our theory
explains observations, many questions remain open. What displacement is necessary to explain
the observations? Why is the energy not dissipated among all thermal modes? What leads us to
reject global or local heating of the solution as an explanation for the diffusion coefficient rise?
We present our theory on enhanced diffusion of enzymes that catalyze exothermic reactions that
addresses these key questions.
30-POS
Board 30
Velocity Control of Dynein-based Transport by Bicaudal D Family Adaptor Proteins
Linas Urnavicius
, Andrew P. Carter.
Medical Research Council, Laboratory of Molecular Biology, Cambridge, United Kingdom.
Most if not all cytoplasmic dynein-1 transport requires the activity of its cofactor dynactin.
Additional proteins, cargo adaptors, are required to stabilize the interaction between dynein and
dynactin. How different cargo adaptors activate dynein is still poorly understood. It was
previously shown in vivo that vesicular transport activated by two Bicaudal D family adaptor
proteins, BICD2 and BICDR-1, differ in velocity, which affects the distribution of transport
carriers. Vesicular transport activated by the BICDR-1 has twice the velocity compared to the
BICD2. We find the same difference in velocity in vitro using a single-molecule motility assay.
In order to understand the control of the velocity of dynein-based transport we combine
engineered complexes based on a 6Å cryo-EM structure of the dynein-dynactin-BICDR-1 and
high spatial-precision measurements of fluorescently labelled complexes to analyse processivity
and stepping behaviour.