Kapitel 12 Flashcards
Endoplasmic reticulum (ER)-resident chaperone protein member of the family of hsp70-type chaperone proteins.
BiP
Carbohydrate-binding chaperone protein in the endoplasmic reticulum (ER) membrane that binds to oligosaccharides on incompletely folded proteins and retains them in the ER.
calnexin
Carbohydrate-binding chaperone protein in the endoplasmic reticulum (ER) lumen that binds to oligosaccharides on incompletely folded proteins and retains them in the ER.
calreticulin
Organelle in green algae and plants that contains chlorophyll and carries out photosynthesis. A specialized form of plastid.
chloroplast
Occurring as translation proceeds. Examples include the import of a protein into the endoplasmic reticulum before the polypeptide chain is completely synthesized (co-translational translocation - Figure 12–32) - and the folding of a nascent protein into its secondary and tertiary structure as it emerges from a ribosome. (Figure 6–79)
co-translational
Contents of a cell that are contained within its plasma membrane but - in the case of eukaryotic cells - outside the nucleus.
cytoplasm
Contents of the main compartment of the cytoplasm - excluding membrane-bounded organelles such as endoplasmic reticulum and mitochondria.
cytosol
Isoprenoid lipid molecule that anchors the precursor oligosaccharide in the endoplasmic reticulum membrane during protein glycosylation.
dolichol
Labyrinthine membrane-bounded compartment in the cytoplasm of eukaryotic cells - where lipids are synthesized and membrane-bound proteins and secretory proteins are made. (Figure 12–33)
endoplasmic reticulum (ER)
Space enclosed by the membrane of the endoplasmic reticulum (ER).
ER lumen
Protein that remains in the endoplasmic reticulum (ER) or its membranes and carries out its function there - as opposed to proteins that are present in the ER only in transit.
ER resident protein
Short amino acid sequence on a protein that prevents it from moving out of the endoplasmic reticulum (ER). Found on proteins that are resident in the ER and function there.
ER retention signal
N-terminal signal sequence that directs proteins to enter the endoplasmic reticulum (ER). Cleaved off by signal peptidase after entry.
ER signal sequence
Membrane proteins anchored in the endoplasmic reticulum (ER) membrane by a single transmembrane α helix contained at their C-terminus.
ER tail-anchored proteins
Ribosome that is free in the cytosol - unattached to any membrane.
free ribosome
Movement of proteins between the cytosol and the nucleus through nuclear pore complexes in the nuclear envelope that function as selective gates.
gated transport
Any protein with one or more saccharide or oligosaccharide chains covalently linked to amino acid side chains. Most secreted proteins and most proteins exposed on the outer surface of the plasma membrane are glycoproteins.
glycoprotein
Mitochondrial membrane that encloses the matrix space and forms extensive invaginations called cristae.
inner membrane
Mitochondrial membrane that encloses the matrix space and forms extensive invaginations called cristae.
inner mitochondrial membrane
One of two concentric membranes comprising the nuclear envelope; contnuous with the outer nuclear membrane; contains specific proteins as anchoring sites for chromatin and the nuclear lamina.
inner nuclear membrane
Compartment of mitochondrion formed between the two concentric mitochondrial membranes.
intermembrane space
Large internal compartment of the mitochondrion.
matrix space
Ribosome attached to the cytosolic face of the endoplasmic reticulum. The site of synthesis of proteins that enter the endoplasmic reticulum. (Figure 12–38)
membrane-bound ribosome
Small vesicle derived from endoplasmic reticulum that is produced by fragmentation when cells are homogenized. (Figure 12–34)
microsome
Part of a multisubunit protein assembly bound to the matrix side of the TIM23 complex that acts as a motor to pull mitochondrial precursor proteins into the matrix space.
mitochondrial hsp70
Proteins first fully synthesized in the cytosol and then translocated into mitochondrial subcompartments as directed by one or more signal sequences.
mitochondrial precursor proteins
Membrane-bounded organelle - about the size of a bacterium - that carries out oxidative phosphorylation and produces most of the ATP in eukaryotic cells. (Figure 1–28)
mitochondrion (plural mitochondria)
Double membrane (two bilayers) surrounding the nucleus. Consists of an outer and inner membrane and is perforated by nuclear pores. The outer membrane is continuous with the endoplasmic reticulum. (Figures 4–9 and 12–7)
nuclear envelope
Bind to both the export signal and nuclear pore complex proteins to guide their cargo through the nuclear pore complex to the cytosol.
nuclear export receptors
Sorting signal contained in the structure of molecules and complexes - such as nuclear RNPs and new ribosomal subunits - that are transported from the nucleus to the cytosol through nuclear pore complexes. (Figure 12–13)
nuclear export signal
Recognize nuclear localization signals to initiate nuclear import of proteins containing the appropriate nuclear localization signal.
nuclear import receptors
Protein subunit of the intermediate filaments that form the nuclear lamina.
nuclear lamin
Fibrous meshwork of proteins on the inner surface of the inner nuclear membrane. It is made up of a network of intermediate filaments formed from nuclear lamins.
nuclear lamina
Signal sequence or signal patch found in proteins destined for the nucleus that enables their selective transport into the nucleus from the cytosol through the nuclear pore complexes. (Figures 12–9 and 12–13)
nuclear localization signal (NLS)
Protein that escorts macromolecules either into or out of the nucleus: nuclear import receptor or nuclear export receptor. (Figure 12–13)
nuclear transport receptor (karyopherin)
Any of a number of different proteins that make up nuclear pore complexes.
nucleoporin
Subcellular compartment or large macromolecular complex - often membrane-enclosed - that has a distinct structure - composition - and function. Examples are nucleus - nucleolus - mitochondrion - Golgi apparatus - and centrosomes. (Figure 1–25)
organelle
Membrane that separates the organelle from the cytosol.
outer mitochondrial membrane
One of two concentric membranes comprising the nuclear envelope; surrounds the inner nuclear membrane and is continuous with the inner nuclear membrane and the membrane of the endoplasmic reticulum.
outer nuclear membrane
Protein translocator in the inner mitochondrial membrane that mediates insertion of inner membrane proteins.
OXA complex
Form a protein translocator that participates in the import of proteins into peroxisomes.
peroxins
Small membrane-bounded organelle that uses molecular oxygen to oxidize organic molecules. Contains some enzymes that produce and others that degrade hydrogen peroxide (H2O2). (Figure 12–27)
peroxisome
mRNA engaged with multiple ribosomes in the act of translation.
polyribosome
Channel-forming proteins of the outer membranes of bacteria - mitochondria - and chloroplasts.
porin
Occurring after completion of translation.
post-translational
Process of transferring a single saccharide or preformed precursor oligosaccharide to proteins.
protein glycosylation
Process of moving a protein across a membrane.
protein translocation
Membrane-bound protein that mediates the transport of another protein across a membrane. (Figure 12–21)
protein translocator
Monomeric GTPase of the Ras superfamily present in both cytosol and nucleus. Required for the active transport of macromolecules into and out of the nucleus through nuclear pore complexes. (Table 15–5 - p. 854)
Ran (Ran protein)
Endoplasmic reticulum with ribosomes on its cytosolic surface. Involved in the synthesis of secreted and membrane-bound proteins.
rough endoplasmic reticulum (rough ER)
Protein translocator that helps β-barrel proteins to fold properly in the outer mitochondrial membrane.
SAM complex
Three-subunit core of the protein translocator that transfers polypeptide chains across the endoplasmic reticulum membrane.
Sec61 complex
Protein-sorting signal that consists of a specific three-dimensional arrangement of atoms on the folded protein’s surface. (Figure 13–46)
signal patch
Enzyme that removes a terminal signal sequence from a protein once the sorting process is complete. (Figure 12–35)
signal peptidase
Short continuous sequence of amino acids that determines the eventual location of a protein in the cell. An example is the N-terminal sequence of 20 or so amino acids that directs nascent secretory and transmembrane proteins to the endoplasmic reticulum. (Table 12–3 - p. 648)
signal sequence
Ribonucleoprotein particle that binds an ER signal sequence on a partially synthesized polypeptide chain and directs the polypeptide and its attached ribosome to the endoplasmic reticulum. (Figure 12–36)
signal-recognition particle (SRP)
Region of the endoplasmic reticulum not associated with ribosomes. Involved in detoxification reactions - Ca2+ storage - and lipid synthesis. (Figure 12–33)
smooth endoplasmic reticulum (smooth ER)
Signal sequence or signal patch that directs the delivery of a protein to a specific location - such as a particular intracellular compartment.
sorting signal
Component in the endoplasmic reticulum (ER) membrane that guides the signal recognition particle to the ER membrane.
SRP (signal-recognition particle) receptor
Short amino acid sequence that enables a polypeptide chain to start being translocated across the endoplasmic reticulum membrane through a protein translocator. Multipass membrane proteins sometimes have both N-terminal (signal sequence) and internal start-transfer signals. (Figure 12–42)
start-transfer signal
Hydrophobic amino acid sequence that halts translocation of a polypeptide chain through the endoplasmic reticulum membrane - thus anchoring the protein chain in the membrane. (Figure 12–42)
stop-transfer signal
(1) “Bedding”: the connective tissue in which a glandular or other epithelium is embedded. Stromal cells provide the environment necessary for the development of other cells within the tissue. (2) The large interior space of a chloroplast - containing enzymes that incorporate CO2 into sugars. (Figure 14–38)
stroma
Flattened sac of membrane in a chloroplast that contains chlorophyll and other pigments and carries out the light-trapping reactions of photosynthesis. Stacks of thylakoids form the grana of chloroplasts. (Figures 14–35 and 14–36)
thylakoid
Protein translocators in the mitochondrial inner membrane. The TIM23 complex mediates the transport of proteins into the matrix and the insertion of some proteins into the inner membrane; the TIM22 complex mediates the insertion of a subgroup of proteins into the inner membrane. (Figure 12–21)
TIM complexes
Multisubunit protein complex that transports proteins across the mitochondrial outer membrane. (Figure 12–21)
TOM complex
The assembly of a translocator associated with other membrane complexes - such as enzymes that modify the growing polypeptide chain.
translocon
Cellular response triggered by an accumulation of misfolded proteins in the endoplasmic reticulum. Involves expansion of the ER and increased transcription of genes that code for endoplasmic reticulum chaperones and degradative enzymes. (Figure 12–51)
unfolded protein response
Transport of proteins from one cell compartment to another by means of membrane-bounded intermediaries such as vesicles or organelle fragments.
vesicular transport
