Secretion system- protein translocation Flashcards
What gram bacteria used the sec system
gram +ive and -ive
What is the purpose of sec system
insert protein in PM or transfer unfolded protein across PM
In which direction are proteins synthesized
in the N to C direction
describe the N and C terminus of proteins
has an unbound amino group and unbound carboxyl group respectively
What does it mean when an amino group is unbound
not convalently linked to the next one
What are other names for the signal peptide
leader peptide or signal sequence
What are proteins w/a signal peptide called
preproteins
what is the hydrophobicity of the central part of the signal peptide
hydrophobic
Describe the signal peptide
proteins translocated by system are synthesized w/25 aa long peptide on N terminal
what is SecB
cytoplasmic chaperone (helper)
what is SecYEG
3 proteins that form an integral PM protein chain or translocase
What is secA
bound to inner surface of SecYEG, an ATPase meaning it hydrolyzes ATP
Where is the signal peptidase located
outer surface of PM
What is the fn of signal peptidase
removes the signal peptide from preprotein
How does secB, the chaperone protein have time to bind
as preprotein is being synthesized signal peptide slows folding of preprotein
What happeds after secB binds to preprotein
inhibits further folding and delivers preprotein to secA, secB is released
How is the signal peptide inserted into the lipid bilayer
N terminius of signal peptide binds to surface of PM and hydrophobic region is inserted into bilayer. remainder of preprotein passes through a pore in SecYEG, at this point most is still in cytoplasm
how is the preprotein released
secA hydrolyzes ATP
how is the rest of the protein translocased to the periplasm
secYEG translocase uses PMF as nrg
How is the signal peptide and protein separated
signal peptidase cuts signal peptidase, protein release into periplasm and folds into its tertiary structure
