Chapter 11: Biological Membranes and Transport

Membranes are much more than just phospholipid

Lipid aggregates

Biological membrane composition

Membrane integral proteins

Computer algorithms are fairly descent at predicting the TM regions within membrane integral protein sequences

Membrane integral proteins

Fluid mosaic model

Fluid mosaic model

Biological transport via vesicle-membrane fusion

Kinetics vs. thermodynamics of transport

Ionophore = chemistry’s Trojan horse.

Diffusion = high to low concentration!

Other types of biological transport

The 2003 Nobel Prize in Chemistry“for discoveries concerning channels in cell membranes”

The potassium channel is an ingenious solution to selectively allowing for potassium, but not sodium

transport

7TMs = GPCRs

Beta-barrel proteins

Three general classes of transport systems

The neurotransmitter/sodium symporter protein family

Yamashita et al., Nature 437, 215-223, 2005.

Phylogenomics of the NSS protein family

Livesay et al., BMC Bioinformatics 8, 397, 2007.

outward open -> occluded -> inward openThis scheme is fairly common

Model of glucose transport into erythrocytes by GluT

Active transport uses ATP hydrolysisto go against the concentration gradient

Oxidative phosphorylation synthesizes ATP, which is driven by the flux of H+ with the concentration gradient

ATPase

The ATP-binding cassette (ABC) transporters and the bacterial periplasmic binding proteins (bPBPs)

bPBP

ATP-binding domains

Transmembrane domains

Substrate

-- Extracellular --

-- Periplasm --

-- Cytosol --bPBP