Transcript Document

S3: “Meet the Molecules”
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Nuclear genes
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ITS = ribosomal internal transcribed spacer
Glu = Polyphenolic adhesive protein
Mitochondrial gene
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CO3 = Cytochrome c oxidase subunit III
The molecules
1. ITS = the internal transcribed spacer of the nuclear
ribosomal genes
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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)
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442
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156
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172
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189
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156
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169
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189
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M. trossulus (~951 bp)
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197
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240
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Restriction sites and fragment lengths for the
Mytilus ITS locus using Hha I restriction enzyme
ITS is under less selection  more variable!
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Reference: Braby & Somero, 2005, Marine Biology
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ITS
M. galloprovincialis (~959 bp)
|
442
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156
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172
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189
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156
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169
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189
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M. trossulus (~951 bp)
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197
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240
442
240
197
The molecules
2.
Glu = Polyphenolic adhesive protein - nuclear
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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
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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
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Safe, natural glue for
surgeries
Coating for medical
implants
Tooth coating for decay
prevention
Anti-biofouling for boats
But synthesis is difficult
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Sticky
Post-translational
modification
Mefp-1 protein
~110 kDa
Ala-Lys-Pro-Ser-Tyr-Hyp-Hyp-Thr- DOPA-Lys
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Decapeptide repeats contain multiple
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Lys = Lysine = electrostatic
Hyp = Hydroxyproline = “sticky”
DOPA = hydroxylated tyrosine = chelator
Repeats vary in number with ≤ 80/protein
Mefp-1 gene
160
474
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2502 bp
Glu primers amplify
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2 products in invader M. galloprovincialis
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~ 300 and 500 bp (shown above)
1 product in native M. trossulus
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654
~ 240 bp
Number of repeats (and therefore gene length) varies
between species
The molecules
3. CO3 = Cytochrome c oxidase subunit III mitochondrial
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One subunit of a large protein in the electron
transport chain
Species level differences are observed after DNA
sequencing
Mitochondria
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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)
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Most ancestral genes lost or
explanted to nucleus
Remaining genes:
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Proteins for respiration
Ribosomal genes
Mitochondrial DNA qualities:
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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/