Transporters

Question 1

What is passive transport?

Answer 1

use energy in the gradient of the ligand to move polar molecules

Question 2

What are examples of passive transporters?

Answer 2

aquaporins, glyceroporin

Question 3

What are the forms of active transport?

Answer 3

1. uniport
2. ATP binding cassette

Question 4

What are uniports?

Answer 4

uniports use electrical potentials “like a magenet” to
a) pull (+) charged ions into the cell
b) force (-) ions out

Question 5

What superfamily falls under uniport?

Answer 5

Major Facilitator superfamily (MFS): use PMF

Question 6

What are two MFS proteins?

Answer 6

1. Ammonia-proton symport (pulls NH3 in)
2. Ammonium-proton antiport (forces NH4 out)

Question 7

What is the “rocker-switch” model?

Answer 7

model that shows how transporters work; outwards vs inward open

Question 8

What is the ATP binding cassete?

Answer 8

importers that use ATP in addition to a signal from a periplasmic binding (PPB) protein to open a transport channel and import a solute

Question 9

the PPB protein makes the transport ________

Answer 9

irreversible

Question 10

What is PTS system?

Answer 10

phosphotransferase system, it phosphorylates glucose (to glucose-6-P) so it cannot diffuse back out

Question 11

Where does phosphate in PTS system come from?

Answer 11

Glycolysis System

1. phosphate group from PEP is transfered to E1
2. P-E1 transfers phosphate to HPr
3. P-HPR transfers phosphate to EIIA
4. P-EIIA interacts with EIIA and EIIC (transporters)
5. EIIB/EIIC phosphorylate glucose

Question 12

What is general secretory pathway?

Answer 12

pathway that bacteria use to secrete proteins or get them out of the cytoplasm

Question 13

How do bacteria get proteins across the inner (cytoplasmic) membrane?

Answer 13

1. SecYEG “translocon” (unfolded proteins)
2. TAT system (folded proteins)

Question 14

How does SecYEG “translocon” work?

Answer 14

1. Cotranslational transport
2. Posttranslational transport

Question 15

How does cotranslational transport work with SecYEG?

Answer 15

1. SRP (signal recognition particle) recognize signal sequence
2. SRP binds to ribosome and takes it to SecYEG (translocon)
3. Ribosome feeds chain of amino acid through translocon into periplasm
   Protein maintaine

Question 16

How does posttranslational transport with SecYEG?

Answer 16

1. Ribosome synthesizes protein
2. Trigger factor (chaperone) binds to polypeptide chain
3. SecB replaces trigger factor, holds protein in unfolded state
4. SecB takes protein to SecYEG
5. SecA (motor protein) forces chain through SecYEG

Question 17

How does TAT system work?

Answer 17

twin argenine transport system

1. TatBC protein embedded in the cytoplasmic membrane recognizes 2 Arg amino acids in substrate
2. TatA is recruited and oligomerize to form a ‘pore’
3. substrate passes through
4. TatA falls apart

Question 18

How do gram negative bacteria, get proteins across outer membrane?

Answer 18

1. Cross both inner and outer membrane in one step (Type I and Type III)
2. Cross membranes individually (Type II)

Question 19

How does Type I transport work?

Answer 19

Drug Efflux pumps use PMF to power transport.
MFP contacts transporter and OMF to hold them together

Question 20

How does Type III transport work?

Answer 20

1. Bacteria contacts host cell
2. protein is secreted directly into host like a syringe