DHFR the MOVIE
The enzyme dihydrofolate reductase (DHFR) catalyzes the reduction of
5,6-dihydrofolate to 5,6,7,8-tetrahydrofolate. A movie depicting
conformational changes of DHFR during one turnover of substrate has
been constructed using six isomorphous crystallographic structures. See
Loop and Domain Movements in the Mechanism of E.
Coli Dihydrofolate Reductase: Crystallographic
Evidence. M. R. Sawaya, & J. Kraut. Biochemistry, Vol
36, pp. 586-603, (1997).
To re-run the movie, click on the Reload button on your Netscape window.
Please click here for a KEY to DHFR's mobile structural elements.
DHFR's REACTION PATHWAY
The sequence of events in this movie was chosen to correspond
to the predominant kinetic pathway of Escherichia coli DHFR under
cellular concentrations of substrates and products. The
pathway was first determined
by Fierke CA; Johnson KA; Benkovic SJ.,
Construction and evaluation of the kinetic scheme associated with
dihydrofolate reductase from Escherichia coli.
Biochemistry, 1987 Jun 30, 26(13):4085-92. The kinetic pathway appears below.
DHFR CRYSTAL STRUCTURES
Six isomorphous crystal structures of E. coli DHFR were solved
(column 2 of table below), each structure analogous to a
complex in the kinetic pathway (column 3 of table below).
The largest motions observed correspond to M20 loop movements
and subdomain movements (columns 4 & 5). These structures
are depicted in the movie above in
frames 01, 24, 25, 44, 51 and 56.
Other frames were generated using the template forcing
algorithm of the program Discover, part of a collection
of programs from MSI. For further details, see
Loop and Domain Movements in the Mechanism of E.
Coli Dihydrofolate Reductase: Crystallographic
Evidence. M. R. Sawaya, & J. Kraut. Biochemistry, Vol
36, pp. 586-603, (1997).
|
Movie Frame |
Crystal Structure Analogue |
Analogous to |
M20 Loop |
Subdomain |
01 |
E*NH |
E*NH |
closed |
open |
24 |
E*FOL*N+ |
E*DHF*NH |
closed |
closed |
25 |
E*MTX*NH |
E*DHF*NH |
closed |
closed* |
44 |
E*ddTHF*ATP-ribose |
E*THF*N+ |
occluded |
open |
51 |
E*ddTHF |
E*THF |
occluded |
closed |
56 |
E*ddTHF*NH |
E*THF*NH |
occluded |
open |
CONSTRUCTION OF DHFR THE MOVIE
The movie,
containing 72 frames, was assembled using GIFMerge . Images
were constructed with the graphics program SETOR written by Stephen Evans
(elmo@nrcbsa.bio.nrc.ca) If you dont have Netscape Version 2.0 or
better and the image below is static you may download an upgraded
version of Netscape
here.
An ENLARGED version of the movie may be viewed with SGI's movieplayer
software. To view the movie, click on
DHFR the MOVIE- SGI.
An ENLARGED version of the movie is also available in MPEG format. Click on
DHFR the MOVIE- MPEG . A special thanks goes
to Sunny Kim for her help in assembling the movie.
If you have any comments about my movie, please click on my email
Michael R. Sawaya (msawaya@ucsd.edu).
A screen should pop up (its self explanatory) and there will be buttons
for send and cancel. You may also wish to visit my homepage.
Some Useful Links to Look At
Michael R. Sawaya
Post Graduate Research Chemist 1995-1996
