Cell bio-Membrane Proteins

MHC proteins of the immune system

Some membrane proteins can serve as recognition proteins, distinguishing self from nonself; give an example

function as 1. enzymes 2. receptors 3. adhesion 4. recognition 5. transport

What are the five functions of membrane proteins

Can be purified by gentle methods that disrupt noncovalent interactions

What is useful about peripheral membrane proteins (protein associated membrane proteins)

beta barrel

a few membrane channels are formed by a beta sheet that is curved into a cylinder; what is this called

single pass alpha helix=receptor protein multi-pass alpha helix=channel forming protein curved beta sheet=channel forming protein

classify the following proteins as a receptor protein or a channel forming protein: single pass alpha helix multi pass alpha helix curved beta sheet

protein associated membrane proteins

these are entirely outside of the membrane and are noncovalently associated with other transmembrane or membrane associated proteins

lipid linked proteins

these are entirely outside the membrane and are covalently attached to a membrane lipid

membrane associated proteins

these proteins are located in the cytoplasm and are anchored to the inner layer of the plasma membrane via an amphipathic alpha helix

transmembrane proteins

these span the entire bilayer

1. resistance to phagocytosis by WBC 2. resistance to flushing 3. attachment to surfaces and to other bacteria

three functions of the glycocalyx in prokaryotes

hydrophobic amino acids

transmembrane alpha helices are composed almost exclusively of ?

kyte-doolitle hydropathy plot

transmembrane domains can be identified by analyzing the amino acid sequence of a protein; useful way to do this?

integral membrane proteins

transmembrane proteins membrane associated proteins and lipid linked proteins all of these are classified as peripheral or integral membrane proteins?

-sodium dodecyl sulfate (SDS)-strong, ionic -triton X-100- mild, nonionic

two common detergents

they have a hydrophobic tail and a hydrophilic head and can form detergent micelles

what does it mean that detergents are amphipathic

positive value goes to a hydrophobic AA negative value goes to a hydrophilic AA

when assigning a hydrophobicity value to AA for a hydropathy plot, which AA get the + value and which the - value

streptococcus mutans which initiates dental cavities by : 1. breaking down sucrose into fructose and glucose 2. breaking down glucose into dextran (which sticks to tooth enamel) using glucosyltransferase

example of prokaryotes using the glycocalyx

that would indicate two membrane spanning alpha helices

if a hydropathy plot indicated two regions of hydrophobicity; what would that indicate

it is composed of secreted carbs rather than carbs covalently attached to a lipid or protein

in prokaryotes, the glycocalyx, or cacpsule, is composed of ?

the free energy required to transfer that amino acid from a nonpolar solvent to water

in step one of hydropathy plot, you assign a hydrophobicity value to each amino acid; what is a hydrophobicity value

1. transmembrane proteins 2. membrane associated proteins 3. lipid linked proteins 4. protein associated membrane proteins

membrane proteins associate with lipid bilayers in what ways

enzymes for : oxidative phosphorylation light dependent reactions of photosynthesis adenylate cyclase enzyme to generate cAMP

membrane proteins can function as enzymes; give examples

Gap junctions-specialized intercellular connection between a multitude of animal cell-types. They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells.

membrane proteins can serve as adhesion proteins; an example includes connexons; what is this proteins function

integrins-link extracellular matrix to cytoskeleton

membrane proteins can serve as adhesion proteins; an example includes integrins; what is this proteins function

desmosomes-a cell structure specialized for cell-to-cell adhesion. A type of junctional complex, they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes

membrane proteins can serve as adhesion proteins; an example is a cadherin; what is this proteins function

claudins and occludins provide tight junction

membrane proteins can serve as adhesion proteins; an example is claudins and occludins; what are the functions of these proteins

insulin receptor EPO receptor nerve growth factor receptor

membrane proteins can serve as receptors, binding extracellular messengers and generating intracellular signals; give examples

1. assign a hydrophobicity value to each amino acid 2. plot each amino acid in the polypeptide chain vs its hydrophobicity value 3. predict the membrane topography of the polypeptide

steps of conducting a hydropathy plot

true

t or f all eukaryotic cells have carbs attached to the plasma membrane

true

t or f cell membranes may be as much as 50% protein by weight

-h. phobic amino acid side groups exposed on outside of helix -polar peptide bonds in polypeptide backbone form H-bonds with each other inside helix

Explain the hydrophobic and hydrophilic anatomy of a membrane spanning alpha helix

porins; these are channel forming proteins in bacteria and the outer mitochondrial membrane

Give an example of a protein that can form a beta barrel

NaK and Ca pump

some membrane proteins provide transport, moving molecules across a lipid bilayer; give an example

glycolipid glycoprotein

carbs covalently attached to membrane lipids?carbs covalently attached to membrane proteins?

1. water-soluble complexes of transmembrane proteins and detergent molecules 2. water soluble mixed lipid-detergent micelles

disruption of a cell membrane by a detergent begins with combining a membrane protein in a lipid bilayer and detergent micelles -what are the results

leukocyte rolling

eukaryotes can use the glycocalyx for cell migration as in the migration of WBC out of the blood vessels; this is called ?

1. protection from mechanical and chemical damage 2. lubrication (in blood cells) 3. specific uses of carbs: -cell migration -cell cell recognition -communication -adhesion -immune responses -blood clotting -molecular targeting

functions of the glycocalyx in eukaryotes

this forms a carb layer around cells called a glycocalyx

glycoproteins and glycolipids almost exclusively face outside the cell, forming ?

face outside of the cell

glycoproteins and glycolipids almost exclusively face which direction in the cell membrane

membrane associated proteins are anchored to the inner layer of the plasma membrane by an amphipathic alpha helix

how are membrane associated proteins anchored to the inner layer of the plasma membrane

These proteins can only be purified by disrupting the ENTIRE membrane with a detergent

how are transmembrane proteins, membrane associated proteins and lipid linked proteins purified

They are peripheral membrane proteins

protein associated membrane proteins are classified as which type of proteins