MICRO 401 Exam 2 UPDATED ACTUAL
QUESTIONS AND CORRECT ANSWERS
What are the types of proteins in the bacterial cell wall? - CORRECT
ANSWER lipoproteins, integral membrane proteins, porins, peripheral membrane
proteins, cell wall attached proteins, periplasmic proteins, secreted proteins
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What are periplasmic associated proteins? - CORRECT ANSWER GLOUBULAR
proteins retained within the periplasmic space in gram - cells and gram + equivalent
What are porins? - CORRECT ANSWER INTEGRAL OUTER MEMBRANE proteins
specific to gram - cells (LPS)
What are secreted proteins? - CORRECT ANSWER proteins secreted into the
environment from the cell
What are peripheral membrane proteins? - CORRECT ANSWER associated with
membrane through GLOUBULAR domains that interact closely with lipids
What are lipoproteins? - CORRECT ANSWER proteins with lipid modifications at the
N termini to embed in the membrane
What are integral membrane proteins? - CORRECT ANSWER proteins that contain 1+
alpha helical transmembrane domains
What are cell wall associated proteins? - CORRECT ANSWER proteins that are
covalently bonded to peptidoglycan, usually at the stem or bridge peptide
major mechanisms/general features/purpose of protein translocation across the cytoplasmic
membrane - CORRECT ANSWER All proteins that function outside of the cytosol
need to translocate to reach their final destinations of secretion outside the cell or exportation
,to the cell membrane and this process requires passage through phospholipid bilayer which is
an energetically unfavorable tprocess so the SEC and TAT systems are used
Purpose of the SEC system - CORRECT ANSWER to transport EXPORTED proteins
such as cell wall associated proteins, integral membrane proteins, periplasmic proteins,
-transports the proteins unfolded states and thread them across the membrane within a protein
channel
Purpose of the TAT system - CORRECT ANSWER to transport SECRETED proteins
outside the cell and this system is only used for proteins that require cofactors [such as
vitamin K., metal ions, etc.]
-the proteins are transported in completely folded or partially folded states
What are the components of the Sec Translocation machinery? - CORRECT
ANSWER -are targeted for export by a characteristic N-terminus of amino acids
-exported proteins have a signal/leader peptide called SP1 that recognizes the overall
topology of the N, H and C regions
-Sec proteins are synthesized at ribosomes in a normal fashion
Describe the TM domain of integral membrane proteins exported by the Sec system -
CORRECT ANSWER The hydrophobic transmembrane domain (central H region) of
INTEGRAL membrane proteins serves as both a Sec substrate signal an as a permanent
structural element
-TM proteins DO NOT have a recognition sequence for SPase
-have an alpha helical domain that is like the H region
Describe the sequence topology for Sec exported substrates - CORRECT
ANSWER The exported proteins have a leader/signal peptide called SP1
-have an N REGION that has + charges AAs to interact with membrane phospholipids
-a central H REGION that is hydrophobic AAs
-a POLAR C REGION that contains the recognition site has a A-X-A motif signal peptidase
that is cleaved by the SPase 1 after transport
, Feature of Sec mediated transport of GLOBULAR proteins via SECB - CORRECT
ANSWER -most globular preproteins are transported via a molecular chaperone to
prevent premature protein aggregation SecB
SecB importance and signal peptide importance - CORRECT ANSWER -SecB is
important to Sec mediated transport of globular proteins because it is the molecular
chaperone
-The signal peptide helps to prevent premature folding and give SecB time to step in and
further prevent folding in the cytosol
How are globular cytoplasmic membrane proteins targeted to the Sec system? - CORRECT
ANSWER they are targeted to the Sec system as ribosome bound nascent chains
(RNCs) by the Signal Recognition Particle (SRP) or by the molecular chaperone SecB
How is pathway a or b chosen in Sec mediated transport? - CORRECT ANSWER this
choice is driven by the hydrophobicity of the emerging peptide
-SRP likes hydrophobic peptides so it like the hydrophobic integral membrane proteins
How does SecB (for globular protein export) recognize sequences? - CORRECT
ANSWER SecB recognizes the unfolded topologies help in common among preprotein
substrates using its two main recognition pockets
describe SecB's main substrate recognition pocket - CORRECT ANSWER -one is lined
with aromatic residues doe the binding of hydrophobic/aromatic regions of polypeptides
-other is an open groove with a hydrophobic surface
Where does SecB go after it binds the globular polypeptide? - CORRECT
ANSWER SecB has a domain that recognizes SecA which is a TRANSLOCASE
COMPLEX embedded in the membrane (SecYEG) that forms a pore channel
How does Sec system get out the cytoplasm? - CORRECT ANSWER The SecYEG
translocase is a pore channel
QUESTIONS AND CORRECT ANSWERS
What are the types of proteins in the bacterial cell wall? - CORRECT
ANSWER lipoproteins, integral membrane proteins, porins, peripheral membrane
proteins, cell wall attached proteins, periplasmic proteins, secreted proteins
"Perfect Pretty Sexy People Love Iced Coffee"
What are periplasmic associated proteins? - CORRECT ANSWER GLOUBULAR
proteins retained within the periplasmic space in gram - cells and gram + equivalent
What are porins? - CORRECT ANSWER INTEGRAL OUTER MEMBRANE proteins
specific to gram - cells (LPS)
What are secreted proteins? - CORRECT ANSWER proteins secreted into the
environment from the cell
What are peripheral membrane proteins? - CORRECT ANSWER associated with
membrane through GLOUBULAR domains that interact closely with lipids
What are lipoproteins? - CORRECT ANSWER proteins with lipid modifications at the
N termini to embed in the membrane
What are integral membrane proteins? - CORRECT ANSWER proteins that contain 1+
alpha helical transmembrane domains
What are cell wall associated proteins? - CORRECT ANSWER proteins that are
covalently bonded to peptidoglycan, usually at the stem or bridge peptide
major mechanisms/general features/purpose of protein translocation across the cytoplasmic
membrane - CORRECT ANSWER All proteins that function outside of the cytosol
need to translocate to reach their final destinations of secretion outside the cell or exportation
,to the cell membrane and this process requires passage through phospholipid bilayer which is
an energetically unfavorable tprocess so the SEC and TAT systems are used
Purpose of the SEC system - CORRECT ANSWER to transport EXPORTED proteins
such as cell wall associated proteins, integral membrane proteins, periplasmic proteins,
-transports the proteins unfolded states and thread them across the membrane within a protein
channel
Purpose of the TAT system - CORRECT ANSWER to transport SECRETED proteins
outside the cell and this system is only used for proteins that require cofactors [such as
vitamin K., metal ions, etc.]
-the proteins are transported in completely folded or partially folded states
What are the components of the Sec Translocation machinery? - CORRECT
ANSWER -are targeted for export by a characteristic N-terminus of amino acids
-exported proteins have a signal/leader peptide called SP1 that recognizes the overall
topology of the N, H and C regions
-Sec proteins are synthesized at ribosomes in a normal fashion
Describe the TM domain of integral membrane proteins exported by the Sec system -
CORRECT ANSWER The hydrophobic transmembrane domain (central H region) of
INTEGRAL membrane proteins serves as both a Sec substrate signal an as a permanent
structural element
-TM proteins DO NOT have a recognition sequence for SPase
-have an alpha helical domain that is like the H region
Describe the sequence topology for Sec exported substrates - CORRECT
ANSWER The exported proteins have a leader/signal peptide called SP1
-have an N REGION that has + charges AAs to interact with membrane phospholipids
-a central H REGION that is hydrophobic AAs
-a POLAR C REGION that contains the recognition site has a A-X-A motif signal peptidase
that is cleaved by the SPase 1 after transport
, Feature of Sec mediated transport of GLOBULAR proteins via SECB - CORRECT
ANSWER -most globular preproteins are transported via a molecular chaperone to
prevent premature protein aggregation SecB
SecB importance and signal peptide importance - CORRECT ANSWER -SecB is
important to Sec mediated transport of globular proteins because it is the molecular
chaperone
-The signal peptide helps to prevent premature folding and give SecB time to step in and
further prevent folding in the cytosol
How are globular cytoplasmic membrane proteins targeted to the Sec system? - CORRECT
ANSWER they are targeted to the Sec system as ribosome bound nascent chains
(RNCs) by the Signal Recognition Particle (SRP) or by the molecular chaperone SecB
How is pathway a or b chosen in Sec mediated transport? - CORRECT ANSWER this
choice is driven by the hydrophobicity of the emerging peptide
-SRP likes hydrophobic peptides so it like the hydrophobic integral membrane proteins
How does SecB (for globular protein export) recognize sequences? - CORRECT
ANSWER SecB recognizes the unfolded topologies help in common among preprotein
substrates using its two main recognition pockets
describe SecB's main substrate recognition pocket - CORRECT ANSWER -one is lined
with aromatic residues doe the binding of hydrophobic/aromatic regions of polypeptides
-other is an open groove with a hydrophobic surface
Where does SecB go after it binds the globular polypeptide? - CORRECT
ANSWER SecB has a domain that recognizes SecA which is a TRANSLOCASE
COMPLEX embedded in the membrane (SecYEG) that forms a pore channel
How does Sec system get out the cytoplasm? - CORRECT ANSWER The SecYEG
translocase is a pore channel
