Membrane fusion

Question 1

sub cellular protein targeting

Answer 1

moving proteins without compromising the membranes’ integrity requires transport vesicles to get from one intracellular compartment to another. Incorrect tranport frequently results in disease (cystic fibrosis due to failure in chloride ion channel protein transport

Question 2

basic principles of membrane and viral fusion

Answer 2

membranes don’t just merge automatically when close. 1)remove water between membranes, 2) overcome charge repulsion of lipids, 3) specificity of membrane fusion

Question 3

What makes up a SNARE protein

Answer 3

VAMPs, syntaxin, and SNAP25

Question 4

VAMPs

Answer 4

transmembrane domain at one end, with a helical domain, all vesicles contain VAMPs

Question 5

Syntaxin

Answer 5

transmembrane domain, helical domain. All target membranes

Question 6

SNAP 25

Answer 6

no transmembrane domain, two helical domains, fatty acid biding region that acts as a membrane binding domain. On All target membranes

Question 7

function of SNARE

Answer 7

Vesicle near target membrane, helical domain on vesicle binds those on target membrane to form an aligned bundle (tetramer), press 2 lipid layers together, squeeze water out, overcome charge repulsion, and promote lipid fusion. Helical binding very strong

Question 8

regulation of SNARE-based fusion

Answer 8

NSF protein twists apart SNARE complex with lots of ATP, Sec1 then refolds syntaxin

Question 9

enveloped viral fusion mechanism

Answer 9

similar to SNARE fusion. Specialized viral fusion protein contains transmembrane domain (insert in viral membrane) and highly hydrophobic fusion domain. Upon receiving specific signal (pH with influenza virus or CD4 with HIV), fusion domain is exposed from the viral protein and inserting into target cell membrane. followed by refolding of fusion protein.