2. Abstract
After cloning cell colonies from the organism Landoltia Punctata,
a strain of duckweed, DNA clone 105KL2.14 coded for a protein
that matched up significantly with another protein involved in
photosynthesis, known as ferredoxin. Plant [2Fe-2S] ferredoxins,
iron-sulfur proteins found on the outside surface of the thylakoid
membrane, serve primarily to transport electrons kept in the iron-
sulfur complex from photosystem I (PSI) to either a lone
thylakoid or to the ferredoxin-NADP+-Reductase enzyme (FNR),
which reduces NADPH. Ferredoxins facilitate reduction of
NADP+ to NADPH.
5. How does it do it?
Ferredoxin, with its [2Fe-2S] cluster, can transport
electrons in it. Photosystem I collects the sunlight and uses
light energy to transfer electrons to the ferredoxin. The iron
in ferredoxin is reduced (gain of electron), and carries that
electron in the cluster until it can hand it off to the FNR
(where the iron is oxidized), which reduces NADP+ to
NADPH with H+ from water. The NADPH is then used in
the Calvin cycle in photosynthesis and then produces
sugar.
8. Differences in Amino Acids
The differences in amino
acids reside all the the
outside corners of the
protein, which makes
sense because those
aren’t very close to the
iron-sulfur cluster, which
is the main region of
activity, making them not
important to the function.
11. Ferredoxin has numerous identical amino acids found in
many plants, as seen in the above diagram, which
directly conveys its vital role in plants; conversely,
organisms from other kingdoms did not show homology
with ferredoxin, with the exception of bacteria. Some
bacteria have bacteria-type Fe4
S4
ferredoxin.
Nonetheless, the matches in ferredoxin found in other
plants implies those amino acids’ vital role in the function
of ferredoxin, maybe to even stabilize the iron-sulfur
cluster.
Homology of Ferredoxin
12. Discussion
With Landoltia Punctata’s starch, another potential use
for this particular strain is biofuel. It is important that
photosynthesis, which produces the starch that is
necessary for the production of biofuel, executes
efficiently. Essentially, the more starch, the higher
quality and more efficient the biofuel will be.
Ferredoxin, the electron-transporter, is vital in the role
of catalyzing photosynthesis and is therefore very
important for this potential use as biofuel.
15. Two iron molecules,
highlighted in orange, and
two Sulfur molecules,
highlighted in yellow,
combine to make the
[2Fe-2S] cluster;
anchoring the the cluster
to the protein are four
cysteines, highlighted in
gold.
Iron-Sulfur Cluster
17. Mutation
Scientists (Benjamin A.Feinberg, Xiaoping Lo, Takeo
Iwamoto, and John M.Tomich) created synthetic mutants of
Clostridium pasteurianum ferredoxin. Several of these
strains involved manipulating the role of cysteine within
ferredoxin and, separately, adding multiple [2Fe-2S]
clusters - all of which, overall, yielded mixed results.
Nonetheless, replacing cysteines within the protein resulted
in a fundamentally more unstable and less efficient
ferredoxin.
18. Conclusion
With Ferredoxin’s essential role in photosynthesis, which is directly
responsible for the massive amount of starch produced by
duckweed, we can conduct further experiments to see if mutating
ferredoxin produces more starch. Since altering any of the
cysteine coordination sites will destabilize the protein, we can try
mutating with other amino acids, to see if it will increase the
efficiency of ferredoxin. If it were to increase the transfer of
electrons in ferredoxin, photosynthesis could occur more
frequently, which yields more starch and in turn, a higher quality of
and a higher volume of biofuel.
19. Kangmin Lee & Robert Mannifield
North Brunswick Township High School
Special Thanks to:
Dr. O’Reilly - NBTHS WSSP Advisor
Dr. Andrew Vershon - Course Instructor
Mr. John Brick - Invaluable Lab Aid
Dr. Janet Mead - Head of Laboratory
Ms. Sue Coletta - Project Coordinator
And the rest of the WSSP Staff
...and to Gerlanda’s and Woody’s for sustenance
![Abstract
After cloning cell colonies from the organism Landoltia Punctata,
a strain of duckweed, DNA clone 105KL2.14 coded for a protein
that matched up significantly with another protein involved in
photosynthesis, known as ferredoxin. Plant [2Fe-2S] ferredoxins,
iron-sulfur proteins found on the outside surface of the thylakoid
membrane, serve primarily to transport electrons kept in the iron-
sulfur complex from photosystem I (PSI) to either a lone
thylakoid or to the ferredoxin-NADP+-Reductase enzyme (FNR),
which reduces NADPH. Ferredoxins facilitate reduction of
NADP+ to NADPH.](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)