EXAM 3 P3 Flashcards
sigma factors
drives expression of genes needed for some particular process by recognizing different promoters
sigma A
housekeeper
sigma N
nitrogen simulation
FiA
flagella synthesis
bacterial transcription
made of a core RNAP plus a sigma factor
-10 and -35 are the recognition sequences
archaeal transcription
single many subunit RNAP
utilizes the TATA site and TATA binding protein
eukaryotic transcription
3 many subunit RNAP
utilizes the TATA site and TBP
gene structure of bacteria
mono or polycistronic
add up to operons and have no introns
gene structure of archaea
mono or polycistronic
no introns
gene structure of eukaryote
only monocistronic and always have introns
characteristics of prokaryotes
little non-coding DNA
no mRNA processing, so it’s ready for translation
transcription and translation are coupled
no nucleus means ribosomes and translation machinery are in the cytoplasm
define coupled transcription and translation
in the cytoplasm
they can happen on the same RNA molecule at the same time
results in very fast production of protein products
only in prokaryotes
characteristics of eukaryotes
lots of non-coding DNA splicing before mRNA can be released into the cytoplasm. transcription is in the nucleus translation is in the cytoplasm no coupling
what is splicing
the first step of mRNA processing. it involves taking the introns out and putting the exons together to forma complete protein coding sequence
other step is adding a 5’ cap on the beginning of mRNA and a poly A tail on the end.
where does splicing occur
in the nucleus
translation
utilizes the universal triplet genetic code
takes place within the ribosomes
starts at the start codon just downstream of RBS. it always encodes insertion of methionine.
terminates at the stop codon
what is a triplet code
3 bases encoding 1 amino acid
ribosomes
a single one contains 3 different rRNA molecules and over 40 proteins
prokaryotic ribosomes
made of a 30S and 50S subunit (=70S)
eukaryotic ribosomes
made of a 40S and 60S subunit (=80S)
rRNA
binds to mRNA, allowing it to find the direct start codon
it creates peptide bonds by putting 2 amino acids together
enzyme is the folded up rRNA
tRNA
decoder between mRNA and the amino acid
looks like an upside down cross
charged with a particular amino acid encoded by that codon
charged with pha found at the acceptor end
anticodon at the tip of the cross binds to the codon of mRNA
shine-dalgarno sequence
aka the ribosome binding site
immediately upstream of the start codon
not used by eukaryotes
N-formyl methionine
unique form of methionine used only by bacteria
found at the beginning of every protein made
stop codons
UAG, UGA, UAA
chaperon proteins
proteins that have the job to help other proteins fold
DNAK/J
take the improperly folded protein and unfold it to go through the process correctly.
utilize ATP for energy
GroEL/ES
chaperone proteins
form a barrel shape with a hydrophobic environment inside and hydrophilic on the outside.
unfolded protein is fed through the barrel and folded properly
utilizes ATP
protein export
last step in getting proteins to their functional location
sec system
used for proteins
looks for a signal sequence found at the beginning of the protein. this is recognized by sec A. it interacts with more proteins here that’ll move it across the mem.
cytoplasmic proteins
those without a signal sequence to be recognized by sec A
sec A
recognizes the signal sequence
binds to the protein and takes it to the membrane
twin-arginine system (TAT)
can export certain fully folded proteins
