Biology 2382B Lecture Notes - Lecture 6: Atp Hydrolysis, Facilitated Diffusion, Membrane Potential
11 Jan 2015
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Document Summary
With the exception of needing phospholipids to form semi- permeable closed compartments, membrane proteins carry out the biological functions of membranes. There are three types and all are asymmetric (in terms of asymmetry in proteins and in phospholipids): Are asymmetric; meaning that they are specifically oriented. Consist of hydrophobic secondary or tertiary structures that span the lipid bilayer. These secondary structures include: helices (approx. 20-25 amino acids) with arg and lys (charged aas) near cytosolic side. They interact with polar head groups: barrels. Proteins anchored to membrane by lipophilic adduct in the following ways: acylation of gly residue of protein. Always on cytosolic side: prenylation of cys residue of protein. Prenylation attaches cys residue at or near c terminus. Always on cytosolic side: glycosylphosphatidylinositol (gpi) anchor. Gpi anchor is always on exoplasmic side and it needs phosphatidylinositol. The polypeptide chain (protein) does not enter bilayer. Also, the lipid-linked proteins have lateral mobility in membrane.
