Completing the Protein life cycle

Question 1

proteins begin to fold even before
their synthesis by is completed

Answer 1

ribosomes

Question 2

is a very crowded place, with
effective protein concentrations as
high as Blank

Answer 2

cytosolic environment, 0.3 g/mL

Question 3

enhances the likelihood of
nonspecific protein association and aggregation

Answer 3

macromolecular crowding

Question 4

the primary driving force for
protein folding is the burial of
Blank away from the aqueous solvent and reduction in solvent-accessible surface area

Answer 4

hydrophobic side chains

Question 5

the folded protein typically has a
buried Blank core and a blank
surface

Answer 5

Hydrophobic, Hydrophilic

Question 6

is driven by hydrophobic interactions, so burial
of hydrophobic regions through
folding is a crucial factor in
preventing aggregation

Answer 6

protein aggregation

Question 7

to evade aggregation, nascent
proteins are often assisted in folding by a family of helper proteins known as Blank

Answer 7

molecular chaperone

Question 8

• abundant proteins in cells given
  brief exposure to high temperature
  (42°C)

Answer 8

Heat shock proteins (Hsps)

Question 9

fold efficiently without the aid of
chaperones

Answer 9

small, single-domain proteins

Question 10

proteins often require chaperones,
especially in the crowded milieu of a cell

Answer 10

larger proteins and multi-domain

Question 11

protein folding by chaperones is
often Blank

Answer 11

ATP-dependent

Question 12

• bind to the chaperone complex and control ATP hydrolysis activity and protein folding

Answer 12

cochaperones

Question 13

in E. coli, the Blank ribosomal protein Blank, which is situated at the peptide exit tunnel, serves as the docking site for TF, directly linking protein synthesis with chaperone-assisted
protein folding

Answer 13

50S ribosomal protein L23

Question 14

Bind to Hydrophobic Regions of Extended Polypeptides

Answer 14

Hsp70 Chaperones

Question 15

• the principal Hsp70 in E. coli
• recognizes exposed, extended regions of polypeptides that are rich in hydrophobic residues

Answer 15

DnaK

Question 16

is energy-dependent and is
driven by ATP hydrolysis

Answer 16

release

Question 17

a Blank that binds polypeptides with exposed hydrophobic regions

Answer 17

18-kDa central domain

Question 18

Blank constitutes 1% to 2% of the
total cytosolic proteins of
eukaryotes, its abundance reflecting its importance

Answer 18

Hsp90

Question 19

• chaperonins
• assists some partially folded
  proteins (10% of the cytosolic
  proteome) to complete folding after
  their release from ribosomes

Answer 19

Hsp60 class of chaperones

Question 20

• found in bacteria

Answer 20

Group I chaperonins

Question 21

• found in archaea and eukaryotes

Answer 21

Group II

Question 22

• group I chaperonin in E. coli

Answer 22

GroES–GroEL complex

Question 23

• made of 2 stacked 7-membered
  rings of 60 kDa subunits that form a cylindrical 14 oligomer 15 nm high
  and 14 nm wide

Answer 23

GroEL

Question 24

• co-chaperonin
• consists of a single 7-membered
  ring of 10 kDa subunits that sits like a dome on one end of GroEL (apical
  end)

Answer 24

GroES

Question 25

• covalent alterations before a
  protein becomes functional
• the primary structure of a protein
  may be altered
• novel derivations may be
  introduced into its AA acid side
  chains

Answer 25

post- translational modifications

Question 26

carbohydrates and lipids may be
covalently attached to a Blank
during its maturation

Answer 26

protein

Question 27

are common mechanisms for regulating protein
function

Answer 27

phosphorylation, acetylation, and
methylation of proteins

Question 28

• the most prevalent form of protein
  post-translational modification

Answer 28

proteolytic cleavage

Question 29

• selectively permeable protein-
  conducting channels that catalyze
  movement of the proteins across
  the membrane, and metabolic
  energy in the form of ATP, GTP, or a membrane potential is essential

Answer 29

translocons

Question 30

• serve as zip codes for sorting and dispatching proteins to their proper compartments

Answer 30

signal sequences

Question 31

• signal sequence-specific
  endopeptidase that proteolytically
  clips the protein once it is routed to its destination

Answer 31

signal peptidase

Question 32

determines the concentrations of
specific proteins expressed within
cells, with protein degradation
playing a minor role

Answer 32

transcriptional regulation

Question 33

• poses a real hazard to cellular
  processes
• compartmentalized, either in
  proteasomes or in lysosomes

Answer 33

protein degradation

Question 34

• the most common mechanism to label a protein for proteasome
  degradation in eukaryotes
  ubiquitin

Answer 34

ubiquitination

Question 35

is transferred from E1 to an SH group on E2, the ubiquitin-carrier protein.

Answer 35

Ubiquitin

Question 36

Ubiquitin has Blank residues, at
positions 6, 11, 27, 29, 33, 48, and 63 K48-type

Answer 36

7 lysine

Question 37

• plays a central role in recognizing and
  selecting proteins for degradation
• selects proteins by the nature of the N-terminal AA
• proteins must have a free -amino terminus to be susceptible

Answer 37

E3

Question 38

• proteins must have a free -amino
  terminus to be susceptible

Answer 38

N-terminal AA

Question 39

• short, highly conserved sequence
  elements rich in pro, glu, ser, thr

Answer 39

PEST sequences

Question 40

• large oligomeric structures
  enclosing a central cavity where
  proteolysis takes place

Answer 40

proteasomes