Lecture 6: Transporters

ABC ATPase

A protein complex that uses ATP hydrolysis to power active transport of substrates across membranes.

Active transport

Transport of molecules across a membrane using energy, against their concentration gradient.

Antiport

A type of transporter that moves two molecules in opposite directions across a membrane.

Chaperone

A protein that helps fold or stabilize other proteins during transport or stress.

Drug efflux pump

A membrane protein system that removes toxic compounds such as antibiotics from inside the cell.

Facilitated diffusion

Passive transport that uses specific carrier proteins or channels to move molecules down their concentration gradient.

MFS transporters

Major Facilitator Superfamily proteins that mediate transport using proton or ion gradients.

Needle complex

A syringe-like structure in Type III secretion systems that injects proteins directly into host cells.

Phosphotransferase system (PTS)

A bacterial transport system that uses phosphate transfer from PEP to import and modify sugars.

Primary active transport

Transport driven directly by ATP hydrolysis (e.g., ABC transporters).

Proton motive force (PMF)

The combined effect of a proton gradient and membrane potential that stores energy for transport and ATP synthesis.

Rocker-switch mechanism

A model of membrane transport where substrate binding causes alternating access of the transporter to either side of the membrane.

Sec translocon (SecYEG)

A protein-conducting channel in the bacterial membrane that exports unfolded proteins.

Secondary active transport

Transport powered by coupling to an existing ion gradient, rather than direct ATP hydrolysis.

Signal peptidase

An enzyme that cleaves signal peptides from proteins after they are translocated.

Signal sequence

A short peptide at the start of proteins that directs them to secretion or membrane insertion systems.

Symport

A transporter that moves two molecules in the same direction across a membrane.

Syringe secretion

Another term for Type III secretion, where proteins are injected into host cells via a needle complex.

TAT secretory system

The Twin-arginine translocation system that exports fully folded proteins across the bacterial membrane.

Type I secretory system

A secretion system that exports proteins directly from the cytoplasm to the outside without periplasmic intermediates.

Type II secretory system

A secretion system that transports proteins from the periplasm across the outer membrane.

Type III secretory system

A secretion system that uses a needle complex to inject effector proteins directly into host cells.

Uniport

A type of transporter that moves a single molecule across a membrane.