Transcript Document
S3: “Meet the Molecules”
Nuclear genes
ITS = ribosomal internal transcribed spacer
Glu = Polyphenolic adhesive protein
Mitochondrial gene
CO3 = Cytochrome c oxidase subunit III
The molecules
1. ITS = the internal transcribed spacer of the nuclear
ribosomal genes
Ribosomal genes code for rRNA
Spacer regions are transcribed but then removed
Region has restriction site polymorphism between species
DNA
RNA
http://fp.bio.utk.edu/my
cology/Techniques/mtwhat_dna.htm
Ribosome
(RNA + proteins)
ITS
DNA
RNA
Ribosome
(RNA + proteins)
http://fp.bio.utk.edu/mycology/Techniques/mt-what_dna.htm
ITS
Multiple copies in genome = many targets for PCR
ITS
(1781-1799)
(1809 bp total)
(303-321)
(1341 bp total)
http://fp.bio.utk.edu/mycology/Techniques/mt-what_dna.htm
ITS
PCR product
M. galloprovincialis (~959 bp)
|
442
|
156
|
172
|
189
|
|
156
|
169
|
189
|
M. trossulus (~951 bp)
|
197
|
240
Restriction sites and fragment lengths for the
Mytilus ITS locus using Hha I restriction enzyme
ITS is under less selection more variable!
Reference: Braby & Somero, 2005, Marine Biology
ITS
M. galloprovincialis (~959 bp)
|
442
|
156
|
172
|
189
|
|
156
|
169
|
189
|
M. trossulus (~951 bp)
|
197
|
240
442
240
197
The molecules
2.
Glu = Polyphenolic adhesive protein - nuclear
Mefp-1 protein
One of the glues that attaches byssal threads to rocks
Number of repeats (and therefore gene length) varies
between species
= repeat
protein
Glu
http://biomaterials.bme.northwestern.edu/mussel.asp
Adhesive proteins anchor
byssal treads to hard
surface
At least five different
proteins
Many variants of each
Most studied foot protein
is Mefp-1
The Mefp-1 gene codes
for the polyphenolic
adhesive protein
Glu
Collagen-like threads with adhesive proteins
http://biomaterials.bme.northwestern.edu/mussel.asp
Glu
DOPA groups (hydroxylated tyrosines) chelate metal ions on surface
http://biomaterials.bme.northwestern.edu/mussel.asp
Novel uses for mussel adhesives
Safe, natural glue for
surgeries
Coating for medical
implants
Tooth coating for decay
prevention
Anti-biofouling for boats
But synthesis is difficult
Sticky
Post-translational
modification
Mefp-1 protein
~110 kDa
Ala-Lys-Pro-Ser-Tyr-Hyp-Hyp-Thr- DOPA-Lys
Decapeptide repeats contain multiple
Lys = Lysine = electrostatic
Hyp = Hydroxyproline = “sticky”
DOPA = hydroxylated tyrosine = chelator
Repeats vary in number with ≤ 80/protein
Mefp-1 gene
160
474
2502 bp
Glu primers amplify
2 products in invader M. galloprovincialis
~ 300 and 500 bp (shown above)
1 product in native M. trossulus
654
~ 240 bp
Number of repeats (and therefore gene length) varies
between species
The molecules
3. CO3 = Cytochrome c oxidase subunit III mitochondrial
One subunit of a large protein in the electron
transport chain
Species level differences are observed after DNA
sequencing
Mitochondria
http://www.bioeng.auckland.ac.nz/images/database/bioinformatics/mitochondria.gif
Organelles involved in
oxidative respiration to
produce ATP
Derived from bacterial
endosymbionts (about
1.2 billion years ago)
Have genome, a circular
DNA molecule (as in
modern bacteria)
Mitochondrial DNA (mtDNA)
Most ancestral genes lost or
explanted to nucleus
Remaining genes:
Proteins for respiration
Ribosomal genes
Mitochondrial DNA qualities:
A haploid genome
Non-Mendelian inheritance
Little or no repair, therefore,
evolves ~ 4 x faster than
nuclear DNA
Useful for evolutionary studies
of closely related species
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Endosymbiosis.html
Cellular respiration
http://pages.slu.edu/faculty/kennellj/
Complex I
Complex II
Complex III
Complex IV
Subunits
NADH
Dehydrogenase
Cytochrome bc1
Succinate
Dehydrogenase
Cytochrome c
Oxidase
mtDNA
7
1
0
3
nDNA
35
10
4
10
TOTAL
42
11
4
13
3D structure of cytochromes
http://dec4.ucdavis.edu/website/Bioenergetics/