6. Transporting Process

Question 1

What are the definitions of Passive transport and Active Transport

Answer 1

Passive Transport: No energy required; moves down a gradient.
Active Transport: Requires energy (ATP); moves against a gradient.

Question 2

Definition

Active Transport

Answer 2

Active transport is the movement of molecules across a membrane using cellular energy (usually ATP) to move substances against their concentration or electrochemical gradient.

JP補足：ATPを使って濃度勾配に逆らう輸送。

Question 3

Passive Transport

Answer 3

Passive transport is the movement of molecules across a membrane without the use of cellular energy, occurring down their concentration or electrochemical gradient.

Question 4

Osmosis

Answer 4

Osmosis is the** passive movement of water **across a selectively permeable membrane from a region of lower solute concentration to higher solute concentration.

Question 5

Transporter

Answer 5

A transporter is a membrane protein that undergoes conformational changes to move specific molecules across a membrane, either passively or actively.

JP補足：形を変えて物質を運ぶタンパク質。

Question 6

Difinition

Uniporter

Answer 6

A uniporter is a transporter that moves one specific type of molecule across a membrane in one direction.

JP補足：単一の物質だけを一方向に運ぶ。

Question 7

Difinition

Cotransporter

Answer 7

Including Symporter and Antiporter
A cotransporter moves two or more different molecules simultaneously across a membrane, with transport coupled.

Question 8

Difinition

Symporter

Answer 8

A cotransporter moving two molecules in the same direction.

Question 9

Difinition

What is an antiporter?

Answer 9

A cotransporter moving molecules in opposite directions.

Question 10

Difinition

Facilitated Diffusion

Answer 10

passive transport in which molecules move across a membrane through** specific transport proteins**, down their gradient.

タンパク質を使うが、ATPを使わない拡散

Question 11

Aquaporin

Answer 11

A water-specific channel protein that increases water transport.

Question 12

What is Ion Pump

Answer 12

a membrane protein that uses energy (often ATP) to move ions across a membrane against their electrochemical gradients.

Question 13

Chemical Gradient

Answer 13

Difference in solute concentration across a membrane.

濃度の差。

Question 14

What is an electrical gradient?

Answer 14

Difference in** charge/electric potential **across a membrane.

Normal Electrical gradient (-70mV)

Question 15

What is an electrochemical gradient?

Answer 15

Combined effect of the chemical and electrical gradients that drives ion movement.

Question 16

What is a channel protein?

Answer 16

a type of integral membrane protein that forms a pore or channel through the cell membrane, allowing specific ions, molecules, or signals to pass through via facilitated diffusion

Question 17

What is ATP-driven active transport (ATP gated)?
List the examples

Answer 17

Type of **Primary acrive transport **using ATP hydrolysis directly to to pump molecules or ions against a gradient.

Ex) Na+ / K+ Pump, Ca+ pump, ABC transporters

ATP分解のエネルギーを直接利用。

Question 18

What is ion gradient–driven active transport?
also list an example.

Answer 18

Secondary active transport powered by the energy stored in an ion gradient (generated by ATP pump) to drive the transport of another molecule against its gradient.

Ex. Na+ / Ca+ pump

ATPを直接使わない！イオンの“流れ落ちる力”を利用して物質を運ぶ。

Question 19

What does the Na⁺/K⁺ pump do?

Answer 19

ATP-dependent antiporter that pumps** 3 Na⁺ ions out of the cell and 2 K⁺ ions in**, maintaining membrane potential (-70 mV) and ion gradients.

3Na⁺を外へ、2K⁺を内へ。ATP使用。

Question 20

What does the** Ca²⁺ pump** do?

Answer 20

The Ca²⁺ pump (Ca²⁺-ATPase) uses ATP to transport Ca²⁺ ions out of the cytosol, usually into the extracellular space or ER, maintaining low cytosolic Ca²⁺ levels.

Question 21

What does the Na⁺/Ca²⁺ exchanger do?

Answer 21

The Na⁺/Ca²⁺ exchanger uses the inward Na⁺ gradient to drive the export of Ca²⁺ from the cell, functioning as a secondary active antiporter.

Na⁺が入る力でCa²⁺を外に出す。ATPは直接使わない。

Question 22

Protein targeting (sorting)

Answer 22

Directing newly synthesized proteins to specific cellular destinations using signal sequences.

新しく作られたタンパク質が どの細胞内区画へ送られるかを決める仕組み。住所ラベル＝シグナル配列で送り先を指定。

Question 23

Secretory route

Answer 23

Pathway where proteins enter the ER, then move through the Golgi to the membrane lysosomes or secretion.

ER→Golgi→細胞外 or 膜 or リソソーム へ向かうタンパク質の運搬ルート。

Question 24

Non-secretory route (pathway)
Also draw the rough picture.

Answer 24

Pathway where proteins remain in the cytosol or go to membrane of organelles, such as mitochondria, nucleus, and peroxisomes (also membrane of ER) without entering the ER.

Question 25

**Signal sequence** Also draw the rough picture

Answer 25

A short peptide that directs a protein to a specific cellular compartment. ## Footnote (→ often 20-50 AA) タンパク質に付いた 配送ラベル（住所）

Question 26

**Signal Recognition Particle (SRP)**

Answer 26

A cytosolic **ribonucleoprotein **complex that binds ER signal sequences and pauses translation for ER targeting (until the ribosome docks at the ER membrane.) ## Footnote ER向けのシグナルを認識して 翻訳を一時停止し、ERへ誘導 する因子。

Question 27

**SRP receptor**

Answer 27

An ER membrane receptor that binds SRP–ribosome complexes to initiate translocation into ER. ## Footnote ER膜にある SRPのreceptor。ここで翻訳が再開し、ER内へ送り込む。

Question 28

**Translocation**

Answer 28

Movement of a newely synthesized polypeptide across a membrane into an organelle such as ER. ## Footnote タンパク質を膜の向こう側へ通すこと。

Question 29

**Signal peptidase

Answer 29

A transmembrane ER enzyme (associated with translocon) that remove (cut) signal sequences after translocation. ## Footnote ERに入った後に シグナル配列を切り取る酵素。

Question 30

**ER signal sequence**

Answer 30

An N-terminal sequence directing proteins to the ER for co-translational import. ## Footnote ER配送専用のシグナル。N末にあることが多い。

Question 31

**Ribonucleoprotein (RNP)**

Answer 31

A complex composed of RNA and protein,such as the SRP. ## Footnote RNA＋タンパク質複合体。SRPもこれ。

Question 32

Topological classes of membrane proteins

Answer 32

Categories describing how membrane proteins span and orient within the lipid bilayer. number of times that its polypeptide chain spans the membrane and the orientation of these membrane-spanning segments within the membrane - How many times a protein spans the membrane - Orientation of its transmembrane (TM) segments Membrane-spanning regions: * Typically 20–25 hydrophobic amino acids forming an α-helix * Hydrophobic side chains face lipid bilayer interior ## Footnote 膜タンパク質が “どちら向き” に、どんな形で膜を貫いているか　＝　構造上の配置 タンパク質が膜を何回貫通するのか？ どの部分が細胞外？どの部分が細胞内？ どんな anchoring（固定）で膜にくっついているのか？

Question 33

Signal-anchor sequence

Answer 33

An internal sequence acting both as an ER signal and a membrane anchor. ## Footnote Type II & IIIに見つかる

Question 34

Stop-transfer sequence

Answer 34

A sequence that halts translocation and anchors the protein in the membrane. ## Footnote Type Iで見つかる

Question 35

ER lumen

Answer 35

The internal space of the ER where protein folding and modification occur.

Question 36

Amphipathic

Answer 36

Having both hydrophobic and hydrophilic regions.

Question 37

Cytosol

Answer 37

The aqueous interior of the cell excluding organelles.

Question 38

Transport vesicle

Answer 38

A membrane-bound vesicle that moves cargo between organelles.

Question 39

Vesicular transport

Answer 39

Transport using membrane vesicles to move proteins and lipids between compartments.

Question 40

Golgi cisterns

Answer 40

Flattened membrane sacs that modify and process transported proteins. 1️⃣ cis-Golgi（シス） ER から来た vesicle を受け取る入口側 タンパクの初期修飾（マンノース除去など） 2️⃣ medial-Golgi（中間） 糖鎖の追加修飾 複雑な glycosylation 3️⃣ trans-Golgi（トランス） 最終的な糖鎖修飾 タンパク質の仕分けが始まる 4️⃣ TGN（trans-Golgi network） 最終仕分けセンター リソソーム行き 分泌経路 細胞膜行き **cis（入り口） → medial（加工） → trans（仕上げ） → TGN（配送）** - なぜ “cisterns” が大事なの？ Because: ✔ 各 cistern は 違う酵素セット を持っていて、 　タンパク質は順に移動しながら加工されていく → **ゴルジ体は「流れベルトコンベア工場」**になっている。

Question 41

Golgi network

Answer 41

Entry (cis) and exit (trans) regions of the Golgi responsible for protein sorting.

Question 42

Endocytosis

Answer 42

Cellular uptake of extracellular material through vesicle formation.

Question 43

List the example of Non-selective Endocytosys

Answer 43

1. **Phagocytosis** - Occurs in specialized cells (e.g., macrophages) - Engulfs large particles or bacteria - Forms **phagosomes** - Actin-dependent and **nonselective** **2. Pinocytosis** - Found in all eukaryotic cells - Nonselective uptake of extracellular fluid and dissolved material

Question 44

Explain the receptor mediated Endocytosis

Answer 44

- Highly specific - A receptor binds a specific ligand → internalization **Examples of internalized ligands:** - **Low-density lipoprotein (LDL)** - **Transferrin** (iron carrier) - **Protein hormones** (e.g., insulin) - **Certain glycoproteins** Mechanism: 1. Ligand binds receptor at plasma membrane 2. Receptor-ligand complex clusters 3. Plasma membrane invaginates 4. Vesicle pinches off and enters the endocytic pathway

Question 45

Importin

Answer 45

A transport receptor that binds NLS-containing proteins and imports them into the nucleus.

Question 46

Exportin

Answer 46

A receptor that exports NES-containing proteins from the nucleus.

Question 47

Ran

Answer 47

A small GTP-binding protein controlling nuclear import and export.

Question 48

Ran-GTP

Answer 48

The active form of Ran that regulates cargo release and receptor binding.

Question 49

Ran-GEF

Answer 49

A nuclear factor converting Ran–GDP to Ran–GTP. ## Footnote GEF: Guanin Exchange Factor

Question 50

Ran-GAP

Answer 50

A cytosolic protein that hydrolyzes Ran–GTP to Ran–GDP.

Question 51

Cargo

Answer 51

A protein with a localization signal transported by importins or exportins. Cargo proteins は、vesicle によって特定の細胞内コンパートメントへ運ばれる「荷物タンパク質」。 配送先はタンパク質がもつ signal sequence（sorting signal）によって決まる。

Question 52

NLS

Answer 52

Nuclear localization sequence directing proteins into the nucleus by binding with Importin A and B

Question 53

NES

Answer 53

Nuclear export signal directing proteins out of the nucleus with Cargocomplex (Ran GTP+Cargoprotein+NES+Exportin 1)

Question 54

Exporter mRNA complex

Answer 54

A complex mediating nuclear export of processed mRNA. (mRNA-hnRNP Complex + CBC(Cap Binding Complex at 5' end))

Question 55

Write the Pathway of Protein Import and Export to the nucleus

Question 56

Write the pathway of mRNA export from nucleus

Answer 56

**III. Export of mRNAs from the Nucleus** **1. 5’ End Leads Transport** - The fully processed **mRNP (mRNA–hnRNP complex)** associates with the **cap-binding complex (CBC)** at the 5′ end. - CBC passes through NPC **first**. --- **2. Removal of Nuclear-Restricted hnRNPs** - Certain hnRNP proteins (orange & dark blue in the diagram) remain **nucleus-restricted**. - These are removed during NPC transport because they **lack NES** → they would otherwise retain mRNA inside the nucleus. --- **3. NES-Containing hnRNPs Mediate Export** - hnRNPs containing **NES** bind export machinery (exportin 1 + Ran·GTP). - They escort the mRNA through the NPC into the cytoplasm. --- **4. Cytoplasmic Events** - Cytoplasmic **RanGAP** triggers GTP hydrolysis by Ran. - Shuttling hnRNPs dissociate from export receptors. - They return to the nucleus for the next cycle. --- **5. mRNA Matures for Cytoplasmic Function** - Freed mRNA associates with cytosolic mRNP proteins. - Example: **Poly(A)-binding protein (PABP)** binds the 3′ poly(A) tail → preparing mRNA for translation.

Question 57

What are the functions of **SPR & SPR Receptor**

Answer 57

1. Help maintain interaction of nascent secretory protein and ER membrane 2. Act together to permit elongation and synthesis of complete protein (only when ER membrane present) 3. Bring ribosomes that are synthesizing secretory proteins to ER membrane

Question 58

Where do the SPR transiently binds to?

Answer 58

1. ER signal sequence 2. Ribosome 3. SPR receptor ## Footnote 6 discrete (indivisual) polypeptide 300 nucleotide RNAでできてる ->

Question 59

What are the three types of protein modification during **secreting pathway**?

Answer 59

1. **Glycosylation:** Addition and processing of carbohydrates (ER & Golgi) 2. **Disulfide bond formation:** Occurs in the ER 3. **Protein folding and assembly:** Occurs in the ER 4. **Proteolytic cleavage:** Occurs in ER, Golgi, and secretory vesicles

Question 60

List the two types of glycoprotein and their characteristics

Answer 60

- **O-linked oligosaccharides** - Attached to **Serine/Threonine hydroxyl groups** - Often short (1–4 sugars) - Seen in **collagen, glycophorin** - **N-linked oligosaccharides** - Attached to **Asn (Asparagine) amide nitrogen -NH基** - CHARACTERISTICS：Larger, branched, complex - WHERE：Initial synthesis occurs in the **ER**

Question 61

What is the structure of precursur of N-linked precursur

Answer 61

- Universal precursor in plants, animals, and yeast: - **3 glucose (Glc)** - **9 mannose (Man)** - **2 N-acetylglucosamine (GlcNAc)** - Total = **14-residue oligosaccharide** - Added as a **preformed block** in the rough ER

Question 62

What is the function of N-linked oligosaccharides

Answer 62

1. Required for **proper folding** in the ER (⇒ Quality Control) 2. Contribute to **stability** of many secreted glycoproteins 3. Essential for **cell–cell adhesion** (e.g., cell-surface glycoproteins) 4. Can **induce immune responses** (e.g., oligosaccharide antigens)

Question 63

During protein modification of secretory pathway, disulfide bond formation is done by

Answer 63

**Protein Disulfide Isomerase (PDI)** ## Footnote abundunt in ER of secretory organs (liver, pancreas) Present in all eukaryotic cells

Question 64

Disulfide bond is formed between

Answer 64

**Cysteins** -SH 基を持っている

Question 65

List the proteins involved in protein folding

Answer 65

1. Chaperon : BiP (Binding Immunoglobulin Protein) 2. Lectines : calnexin, calreticulin 3. PDI (protein disulfide isomerase) : disulfide bridge formation 4. Oligosaccharyl transferase: glycosylation 5. Peptidyleprolyl isomerase: prolin cis-trans transformation

Question 66

secretory pathwayの流れを書く

Answer 66

## Footnote ノート参照

Question 67

Cisterna progression

Answer 67

cisterna physically moves through the Golgi. cis-, medial-, trans- Golgi to trans-Golgi network ## Footnote No involving **Anterograde vesicle** **Retrograde Vesicle** continuilly retreive residents enzyme back to earlier

Question 68

What are the three pathway of trans-Golgi network

Answer 68

1. Contistitutive secretion: - Vesicles fuse with the **plasma membrane immediately** - Continuous secretion in all cells 2. Regulated Secretion: - Proteins are packaged into **secretory vesicles** - Vesicles remain stored inside the cell - Fusion with plasma membrane occurs **only upon receiving a signal** 3. Delivery to Lysosomes: - Vesicles move from TGN → **late endosome** - Transport from late endosome → lysosome likely via **direct fusion**

Question 69

# thre List the types of coated vesicles

Answer 69

**1. COPII** - **ER → Golgi** (anterograde) **2. COPI** - **Retrograde:** - Golgi → ER - trans-Golgi → medial-Golgi → cis-Golgi (retrieval) **3. Clathrin** - **Plasma membrane → late endosome** - **TGN → late endosome** *Note:* Coat for TGN → plasma membrane (constitutive/regulated secretion) is **not yet identified**

Question 70

Write the pathway of protein from ER to TGN and their branch pathway

Answer 70

ER → COPII vesicles → cis-Golgi → medial-Golgi → trans-Golgi → TGN ↑ ↓ |—— COPI retrieval ————————| From TGN: 1. Constitutive secretion → plasma membrane 2. Regulated secretion → secretory vesicles → signal-dependent exocytosis 3. Lysosomal pathway → late endosome → lysosome Endocytosis: - Receptor-mediated → early endosome → late endosome → lysosome OR recycling to surface

Question 71

List Four Topological Classes of Integral Membrane Proteins

Answer 71

**Type I** - **Single-pass** - **N-terminus in lumen**, C-terminus in cytosol - Contain: – N-terminal **cleavable signal sequence** – Internal **stop-transfer anchor** = TM α-helix - Signal sequence initiates import → cleaved → stop-transfer halts translocation → TM domain inserted laterally into membrane **Type II** - **Single-pass** - **N-terminus in cytosol**, C-terminus in lumen - Have a single **internal signal-anchor**, not cleaved - Internal signal-anchor: – Acts as ER signal – Acts as membrane anchor - Positively charged residues on **N-terminal side** → keep N-terminus in cytosol ## **Type III** - **Single-pass** - **N-terminus in lumen**, C-terminus in cytosol (opposite of Type II) - Internal signal-anchor near the N-terminus - Signal-anchor also acts as **stop-transfer** - Positively charged residues on **C-terminal side** determine orientation **Type IV (Multipass)** - Multiple TM helices - Two subtypes: **Type IV-A** - **N-terminus in cytosol** - Pattern: – First TM helix = Type II–like internal signal-anchor – Second TM helix = stop-transfer – Subsequent helices alternate signal-anchor and stop-transfer - Examples: GLUT transporters, many ion channels **Type IV-B** - **N-terminus in lumen (exoplasmic space)** - Hydrophobic TM helix near N-terminus + cluster of positive charges → Type III–like orientation - Insertion uses alternating signal-anchor and stop-transfer sequences - Example: GPCRs (7-pass)

Question 72

Explain GPI-Anchored Proteins

Question 73

What is the import machinary of mitochondria

Answer 73

**Matrix-Targeting Sequence** - Location: N-terminus - Length: 20–50 aa - Structure: amphipathic α-helix – One side: positively charged residues – Other side: hydrophobic residues **Import Machinery** **Outer Membrane** - Receptors: **Tom20**, **Tom22** - Channel: **Tom40** **Inner Membrane** - Channel: **Tim23/Tim17** - Import occurs at **contact sites** - Matrix protease cleaves targeting sequence - Final folding often requires chaperonins ## Footnote Tom: Translocon of Outer Membrane Tim: Translocon of Inner Membrane

Question 74

What are requred to import protein into mitochondria genellary

Answer 74

1. Energy 2. Proteins (unfolded) => Cystolic Hsc 70 keeps protein unfolded

Question 75

What binds directly to the NLS on a cargo protein?

Answer 75

Importin α binds directly to the NLS.

Question 76

Which two proteins cooperatively bind a cargo protein to form the trimeric import complex?

Answer 76

Importin α and importin β.

Question 77

Which part of the import complex interacts with NPC components to mediate translocation?

Answer 77

Importin β.

Question 78

What energy source is required for import through the nuclear pore complex?

Answer 78

ATP hydrolysis.

Question 79

What molecule in the nucleoplasm causes dissociation of the import cargo complex?

Answer 79

Ran·GTP.

Question 80

What happens when Ran·GTP binds importin β?

Answer 80

The import cargo complex dissociates and the cargo is released.

Question 81

What protein stimulates conversion of Ran·GTP to Ran·GDP in the cytoplasm?

Answer 81

RanGAP.

Question 82

After Ran·GTP is hydrolyzed to Ran·GDP, what happens to importin β?

Answer 82

It dissociates from Ran·GDP and can initiate another import cycle.

Question 83

Which nuclear factor converts Ran·GDP back to Ran·GTP?

Answer 83

RCC1 (Ran nucleotide-exchange factor).

Question 84

What binds to the NES of a cargo protein to initiate export?

Answer 84

Exportin 1.

Question 85

What molecule binds cooperatively with exportin 1 and the NES during nuclear export?

Answer 85

Ran·GTP.

Question 86

What causes dissociation of the export complex in the cytoplasm?

Answer 86

RanGAP-mediated conversion of Ran·GTP to Ran·GDP.

Question 87

What happens to the NES-containing cargo after export complex dissociation?

Answer 87

It is released freely into the cytosol.

Question 88

Where are exportin 1 and Ran·GDP transported after dissociation in the cytoplasm?

Answer 88

Back into the nucleus through NPCs.

Question 89

Which protein complex binds the 5′ end of mature mRNA to enter the NPC first?

Answer 89

The cap-binding complex (CBC).

Question 90

Why must certain hnRNP proteins be removed during passage through the NPC?

Answer 90

Because they lack NES and would retain mRNA in the nucleus.

Question 91

What allows NES-containing hnRNPs to escort mRNA through NPCs?

Answer 91

They use the exportin 1 + Ran·GTP nuclear export mechanism.

Question 92

What triggers dissociation of shuttling hnRNPs from export receptors in the cytoplasm?

Answer 92

RanGAP-induced hydrolysis of Ran·GTP.

Question 93

After export, what protein binds the 3′ poly(A) tail of mRNA?

Answer 93

Poly(A)-binding protein (PABP).

Question 94

v-SNARE

Answer 94

(vesicle-SNARE) A membrane protein located on the transport vesicle that specifically pairs with a t-SNARE on the target membrane to mediate membrane fusion. ## Footnote on vesicle, fusion

Question 95

t-SNARE

Answer 95

(target-SNARE) A membrane protein located on the target organelle or plasma membrane that binds to the matching v-SNARE, ensuring specific vesicle docking and fusion. ## Footnote on target membrane, recognizes vesicle

Question 96

COP II

Answer 96

(Coat Protein Complex II) A protein coat that drives budding of transport vesicles from the rER to the cis-Golgi — responsible for anterograde transport. ## Footnote ER ➜ Golgi

Question 97

COP-I

Answer 97

(Coat Protein Complex I) A protein coat that mediates retrograde transport — returning proteins and membranes from the Golgi back to the ER, or between Golgi cisternae. ## Footnote Golgi ➜ ER

Question 98

clathrin

Answer 98

A coat protein that forms triskelion-shaped structures, driving vesicle formation involved in endocytosis, and transport from the trans-Golgi network to endosomes and lysosomes. ## Footnote endocytosis & TGN sorting

Question 99

sorting signal

Answer 99

A short, specific amino acid sequence within a protein that directs it to its correct cellular destination by interacting with sorting receptors during vesicular transport. ## Footnote address label (Signal Sequence)

Question 100

WAMP

Answer 100

(Vesicle-Associated Membrane Protein) A major v-SNARE protein found on transport vesicles that pairs with t-SNAREs to drive membrane fusion specificity. (If your slide said “WAMP,” it's almost certainly referring to VAMP.)

Question 101

Quality control in the ER N-linked and O-linked oligosaccharides

Answer 101

A surveillance system in the rough ER that ensures only properly folded and correctly glycosylated proteins proceed to the Golgi. Misfolded proteins are retained, refolded, or degraded through ER-associated degradation (ERAD).

Question 102

N-linked Oligosaccharides

Answer 102

A carbohydrate chain attached to the amide nitrogen of Asn in the consensus sequence Asn-X-Ser/Thr. They are assembled first on dolichol in the ER and play major roles in protein folding and quality control.

Question 103

O-linked Oligosaccharides

Answer 103

Carbohydrate chains attached to the hydroxyl group of Ser or Thr residues. They are added in the Golgi apparatus, usually forming short, linear sugar chains.

Question 104

protein disulfide isomerase

Answer 104

An enzyme in the ER lumen that catalyzes the formation, reduction, and rearrangement of disulfide bonds, allowing newly synthesized proteins to achieve correct tertiary structure.

Question 105

lectin: calnexin,calreticulin

Answer 105

ER-resident lectins that bind monoglucosylated N-linked oligosaccharides on newly made proteins. They retain partially folded proteins in the ER and promote proper folding as part of the calnexin/calreticulin cycle. Calnexin — membrane-bound lectin Calreticulin — soluble ER-luminal lectin Both ensure only correctly folded glycoproteins exit the ER.

Question 106

Tom (the outer membrane translocon)

Answer 106

(Translocase of the Outer Membrane) A protein complex in the outer mitochondrial membrane that recognizes mitochondrial targeting sequences and mediates the initial import of nuclear-encoded mitochondrial proteins.

Question 107

Tim (the inner membrane translocon)

Answer 107

(Translocase of the Inner Membrane) A protein complex in the inner mitochondrial membrane that works with TOM to translocate polypeptides into the mitochondrial matrix or insert them into the inner membrane.