Protein Components of Membranes & their Function Flashcards
3 Membrane Proteins
integral, lipid-anchored, & peripheral
glycolipid
glycosylated lipid; only found on exterior leaflet of membrane
Glycophorin A
transmembrane protein found on red blood cells; homomeric protein w/ coiled coil motif
homomeric protein
2 of the same proteins combined to form quaternary structure
Ion Channel Structure
tetrameric, hydrophobic aa on exterior, hydrophillic aa on interior
Types of transmembrane proteins
ion channels & porins
porin
channel for water & sugars; generally made of beta sheets
3 lipid anchored proteins
GPI anchor, Acylation, & Prenylation
GPI
glycosyl phospha tidyl inositol
GPI-anchor
phosphatidylinositol contains two fatty acyl chains extended into bilayer, phosphoethanolamine links to C-terminus of protein, & sugar residues
Acylation
cytosolic v-Src proteins; single fatty acyl chain attaches to N-terminal Glycine residue of polypeptide
Prenylation
cytosolic Ras & Rab proteins; hydrocarbon chain attaches to Cysteine residues near C-terminus
Acylation lipid anchors
myristate & palmitate
Prenylation lipid anchors
farnesyl & geranylgeranyl
glycosylation
addition of carbohydrate (sugar) chains to a protein; occurs on exoplasmic domain of most transmembrane & peripheral proteins
carbohydrate group function
interact with extracellular matrix, growth factors, antibodies, etc
Pleckstrin Homology (PH) Domain
most common lipid binding motif in peripheral membrane proteins; associates with phosphorylated inositols
hypotonic
ion/solute concentration lower on outside/higher on inside; water moves inside
hypertonic
ion/solute concentration higher on outside/lower on inside; water moves outside
Common Functions of the Cell Membrane
junctions between cells (adherence & exrtacellular signaling) & cell surface receptors to bind signaling molecules
