Lecture_4_Jan_11_four_slides_per_page_ - Composition of...

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1 Membrane Protein (reading assignment: 125-136, 629-636) Composition of Biological Membranes cell or organelle membrane leaflet A biological membrane is a lipid bilayer composed of two leaflets of lipids For most membranes: 50% protein content For myelin membrane: 25% protein content For mitochondrial inner membrane: 75% protein content A membrane has two major components: proteins and lipids Lipids account for the permeability barrier of a membrane (as discussed before) Membrane proteins account for most of the specific activities of a membrane Membrane Proteins different types of membrane proteins (unlike lipids which are always an integral part of a membrane, a protein may how to analyze different types of membrane proteins (p yg p , p y associate with a membrane in different ways) how to study membrane proteins Three Major Types of Membrane Proteins integral membrane proteins: part of a protein amino acid sequence spanning the hydrophobic part of a lipid bilayer pgy p p p y
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2 Integral Membrane Proteins three transmembrane helix anchored (transmembrane domain: the domain of a protein which spans the lipid bilayer) Most integral membrane proteins contain at least one transmembrane domain The transmembrane domain of an integral membrane protein usually adopts either an alpha-helix (as in 1, 2, and 4) or a beta-barrel structure (as in 3) as alpha-helices (rare, not really transmembrane) single transmembrane as an alpha-helix multiple transmembrane as a beta-barrel (a hydrophilic pore in the center of barrel) What determines the alpha-helix v.s. beta-strand?
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This note was uploaded on 02/01/2010 for the course MCDB 103 taught by Professor Staff during the Winter '08 term at UCSB.

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Lecture_4_Jan_11_four_slides_per_page_ - Composition of...

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