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Lecture 5

Lecture 5 CSB351 Virology

3 Pages

Cell and Systems Biology
Course Code
Mounir Abou Haidar

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(1) Lipids, Carbohydrates, Polyamines--p. 22
All three: not all virus have these
Last time
Lipids and carbohydrates: essential for infectivity
Some lipids interact with proteins = lipoproteins
Lipids not synthesized by virus: simply taking a piece of membrane itself
Enveloped viruses have lipids--> lipids are soluble to organic solvents(i.e. Oil, alcohol), therefore, if wash hands with 70% alcohol, destroy
viruses with envelopes
If destroy envelopes: virus dead--> glycoproteins on envelope is how virus attaches to the cell
BUT some viruses (Hepatits A): no envelopes--> alcohol doesn't affect them
Lipid containing viruses: usually released from infected cells by a "budding" process
Similarities between cell membrane and viral envelope--> Viral membrane mostly originate from cell membrane
Viral lipids same as cell lipids: cholesterol, phospholipids (sphingomyelin, phosphatidylcholine, phosphatidylserine, etc)--> found in
CERTAIN viruses (enveloped)
Budding process: once you put sugar on protein --> = putting zip code on letter, straight to membraneof the cell
Cells have machinery that put sugar on protein, virus knows glycosylation signal
Viruses that don't have envelope: don't bud, but lyse cell and kills it ---> those that do: bud out and take a piece of membrane with it
Viral proteins interact with viral lipids: bonds are hydrophobic & H-bonds (no covalent)
Most are involved in the infectivity process: glycoproteins on membrane--> "spikes" on envelope--> destroy this, destroy glycoprotein-->
thus lipids contribute to stability of viral envelopes
How does a virus anchor itself into the membrane of the cell?
Protein has in the middle of them: a lot of Leucine --> hydrophobic amino acid --> Leucine comes in contact with membrane (lipid bilayer)
On the outer membrane of the cell: cell has HA and NA
Virus comes through the cell, bud, take cell membrane with it, now virus has NA and HA in its envelop
Metals &Polyamines
Some viruses contain polyamines (spermine, spermidine, putrescine, etc)
(+) charged: they have Lys (K) and Arg -->Neutralize( -) charge of phosphates in NA
Play important roles in many proteins
Pages T2 and T4: contain putrescine associated to DNA
(2) Characterization of viruses: General principles, techniques, (ignore "some purification
techniques"), etc--P. 25
Big stuff: nucleus stuff are found at the bottom of the tube
Supernatant on top of the "bead": supernatant that includes soluble proteins and virus (still swimming)
Viruses are much bigger than soluble proteins --> use this property to separate them from the rest of the proteins in the
Then: now you have nuclei and cell debris and organelles --> take big mess, put in centrifuge, spin
ALL Vs generally degraded by extreme pH, high temp and high salt
Precipitate specifically to the properties of the virus--> increase weight of molecule artificially, by spinning it around in a centrifuge
Put virus from supernatant into tube and spin--> generate centrigufal force
Viruses are largely formed of proteins--> tech used for purification of ptns are also used to prepare Vs
Vs usually possess a defined size, shape, and density--> serve as a basis for separation, depending on one of more of these properties
In any purification method, need to consider stability of V to that particular treatment
Consider 3 things:
F = force applied to molecules
f = frictional coefficient (shape) sphere or rod, viscosity of medium
F = f * (velocity of molecules)
Lecture 5
2:05 PM
CSB351 Course Notes Page 1

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Lecture5 September-29-09 2:05PM (1)Lipids, Carbohydrates,Polyamines--p. 22 { Allthree:notallvirushavethese Carbohydrates { Lasttime Lipids { Lipidsandcarbohydrates:essentialforinfectivity { Somelipidsinteractwithproteins=lipoproteins { Lipidsnotsynthesizedbyvirus:simplytakingapieceofmembraneitself Someviruses(paramyxovirusese.g.measles)containlipidsandglycoproteins-->componentsformviralenvelopes(Glycoproteinsformthe spikes,whichprojectfromthevirusparticle.) Envelopedviruseshavelipids-->lipidsaresolubletoorganicsolvents(i.e.Oil,alcohol),therefore,ifwashhandswith70%alcohol,destroy viruseswithenvelopes Ifdestroyenvelopes:virusdead-->glycoproteinsonenvelopeishowvirusattachestothecell BUTsomeviruses(HepatitsA):noenvelopes-->alcoholdoesntaffectthem { Lipidcontainingviruses:usuallyreleasedfrominfectedcellsbyabuddingprocess Similaritiesbetweencellmembraneandviralenvelope-->Viralmembranemostlyoriginatefromcellmembrane Virallipidssameascelllipids:cholesterol,phospholipids(sphingomyelin,phosphatidylcholine,phosphatidylserine,etc)-->foundin CERTAINviruses(enveloped) Buddingprocess:onceyouputsugaron protein-->=puttingzipcodeon letter,straighttomembraneofthecell Cellshavemachinerythatputsugaronprotein,virusknowsglycosylationsignal Virusesthatdonthaveenvelope:dontbud,butlysecellandkillsit--->thosethatdo:budoutand takeapieceofmembranewithit { Viralproteinsinteractwithvirallipids:bondsarehydrophobic&H-bonds(nocovalent) { Mostare involvedintheinfectivityprocess:glycoproteinsonmembrane-->spikesonenvelope-->destroythis,destroyglycoprotein--> thuslipidscontributetostabilityofviralenvelopes { Howdoesavirusanchoritselfintothemembraneofthecell? Proteinhasinthemiddleofthem:alotofLeucine-->hydrophobicaminoacid-->Leucinecomesincontactwithmembrane(lipidbilayer) Ontheoutermembraneofthecell:cellhasHAand NA Viruscomesthroughthecell,bud,tak
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