Transmembrane Structures

single transmembrane helix

helix bundle

e.g. gram positive bacteria

membranes are hydrophobic, so residues will be hydrophobic too. membrane size is 30, need 20 alpha helix res.

need hydrophobic values per amino acid, use sliding window

positive inside: + charge are inside cell (cytoplasmic), so this end Arg, Hys, Lys

e.g. G-Protein receptors (signal transduction). 7 helix bundle. responds to light, metal ions, organic molecules, small proteins

beta barrel

e.g. gram negative bacteria

e.g. porins, allow nutrients + waste to cross though. outside barrel hydrophobic, inside hydrophilic. aromatic at head of membrane. trimer. passively allows small hydrophilic molecules. outer membrane only of bacteria

membrane associated


transport: pump, transporter, ion channel

receptors: ligand binding (signal recognition), signal transmission (via membrane), signal response (intracellular)

cell tissue stabiliser.