2-transcription, translation
Biology 518 with Scot Hefty/susan Egan at University of Kansas
About this deck
By: crystal mccowen
Textbook:
Molecular Genetics of Bacteria (Snyder, Molecular Genetics of Bacteria)
Created: 2011-12-13
Size: 33 flashcards
Views: 1
Textbook:
Molecular Genetics of Bacteria (Snyder, Molecular Genetics of Bacteria)Created: 2011-12-13
Size: 33 flashcards
Views: 1
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overview of 7 steps of transcription
- sigma binds RNAP
- promoter recognition
- isomerization
- initiation
- promoter escape
- elongation
- termination
RNAP holoenzyme subunits:
a2BB'w + SIGMA
highly conserved part of RNAP
Mg2+ active site
sigma recognizes promoter's consensus sequences, which consist of ____. Which sigma domains recognize which regions?
-10 and -35
sigma domain 2 recognizes -10
sigma domain 4 recognizes -35
sigma-70 also known as
house-keeping sigma
UP elements
present in strong promoters
upstream of -35have AT-rich regions
alpha-CTD of RNAP binds to it==>strengthens RNAP-DNA binding
promoters with extended -10 regions are recognized by ______
sigma domain 3
often have weak or no -35 at all
what occurs during isomerization step of transcription?
AT-rich regions of -10 in promoter unwind to form OPEN COMPLEX
formation of open complex stabilizes RNAP on DNA by closing its "jaws"
during transcription initiation, what happens?
first nucleotides added at +1 position
abortive initiation
what is abortive initiation?
sigma-3.2 blocks RNA from exiting RNAP
short RNA products eventually knock it out of the way so elongation can continue past 10bps
what occurs during promoter escape
RNAP breaks all contacts with promoter, sigma is released
does RNAP require helicase?
no, it does the unwinding itself
two types of transcription termination
factor independent(most common)
rho dependent
describe factor independent termination
hair loop followed by series of U's in RNA after open reading frame
weakens RNA-DNA hybrid==>RNA pulled out, RNAP disassembles
describe rho-dependent termination
- when RNA rut sites exits the RNAP, rho protein binds to it (before ribosome covers it up)
- rho uses ATP-energy to move up mRNA toward RNAP
- once RNAP has reached the rho-sensitive pause site on DNA, it pauses
- rho pulls out the RNA from RNAP
- RNAP disassembles
what is a rut site?
rho-utilization site
on RNA
where rho binds
polarity?
mutation in one gene of operon affects expression of other genes in operon
describe an alpha helix
secondary structure
3.6 AA/turn
h-bonds between one AA and another AA 4 residues down
what is DnaK and how does it work?
chaperone of heat shock family
binds hydrophobic regions in ATP-DEPENDENT MANNER of nascent proteins to prevent aggregation
what are GroEL/GroES
GroEL=chaperonin
GroES=cochaperonin cap
how does GroEL work?
- protein enters cylindrical GroEL
- GroES cap assembles on GroEL w/ help of ATP
- GroEL uses ATP to help protein fold
- protein, GroES cap leave
- next unfolded protein enters on other side of GroEL
translation start/ stop codons
start: AUG
stop: UAA,UAG,UGA
AUG encodes...
formyl-Met
charging of t-RNAs accomplished by...
amino-acyl-tRNA synthetase
uses ATP
2 types of f-Met processing (after translation)
1. just remove formyl group
2. remove entire f-Met AA
describe steps of translation initiation
- IF3 binds 30S to prevent association w/ 50S
- IF1 binds A-site of 30S to prevent tRNA binding
- RNA binds 30S
- IF2(GTP) brings charged f-Met-tRNA to P-site
- IF1/IF3 released
- IF2 hydrolyses GTP, is released
- 50S assembles ==> 70S INITIATION COMPLEX
what are the 3 general steps of translation elongation?
1. AA-tRNA binds A-site
2. peptide bond formation
3. translocation of ribosome to next codon
describe how charged-tRNA binds A-site of ribosome
1. EF-Tu(GTP) brings AA-tRNA to A-site
2. EF-Tu hydrolyzes GTP ==>EF-Tu released
3. EF-Ts recycles EF-Tu to GTP-bound form
describe peptide bond formation in ribosome
peptidyl-transferase activity of ribosome==>peptide bond
peptide chain ends up on AA in A-site
energy for peptide bond comes from cleavage of AA-tRNA bond
describe translocation of ribosome to next codon
EF-G(GTP) hydrolyzes GTP ==>translocation
describe roles of RF factors in translation termination
- RF3 brings either RF1 or RF2 to stop codon at A-site
- RF1 for UAA and UAG
- RF2 for UAA and UGA
- RF1 and RF2 are both ATP-bound
- ATP-hydrolysis ==> breaks peptide-tRNA bond ==>protein released
coupling of transcription/translation by ___
NusG
interacts w/ both ribosome and RNAP
describe polycistronic mRNA
translation of open reading frames in an operon are
independent
simultaneous
separate
About this deck
By: crystal mccowen
Textbook: Molecular Genetics of Bacteria (Snyder, Molecular Genetics of Bacteria)
Created: 2011-12-13
Size: 33 flashcards
Views: 1
Textbook:
Molecular Genetics of Bacteria (Snyder, Molecular Genetics of Bacteria)Created: 2011-12-13
Size: 33 flashcards
Views: 1
About StudyBlue
STUDYBLUE makes things that make you better at school.
Things like online flashcards with photos and audio.
Things like personalized quizzes and friendly reminders about when (and what) to study next.
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STUDYBLUE exists to make studying efficient and effective for every student, for free. Join us.
“Simply amazing. The flash cards are smooth, there are many different types of studying tools, and there is a great search engine. I praise you on the awesomeness.”
Dennis
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