chapter 13.1-13.2 Flashcards
the processes of translation and translocation are done….
simultaneously
what is SRP
signal-recognition particle that recognizes the N-terminus signal on the newly translated protein and brings the protein-ribosome complex to the SRP receptor in the ER membrane
what is the translocon
a channel protein that allows for the continual translation of the protein on the ribosome through the membrane and into the ER lumen
what does signal peptidase do
cleaves the N-terminus signal sequence
what is the role of sec61
yeast translocon component that allows for the post-translational translocation
what are topogenic sequences
N-terminus signal sequences, internal stop-transfer anchor sequences, and internal signal-anchor sequences
what do topogenic sequences do
direct the insertion of nascent proteins into the ER membrane
how can membrane protein topology be predicted
by computer programs that identify hydrophobic topogenic segments within the primary amino acid sequence
what are type 1 ER membrane proteins
single pass proteins with an N-terminus signal sequence
what are type 2 ER membrane proteins
basically the opposite of type 1
no N-terminus signal sequence, have a lysine/arginine section that puts the N-terminus end in the cytosol and the C-terminus end in the ER lumen
what are type 3 ER membrane proteins
single pass proteins where the N-terminus end goes into the ER lumen and the C-terminus end stays in the cytosol
what happens with a tail-anchored protein
there is a hydrophobic C-terminal tail on the protein that Get3 recognizes and brings to the Get complex
with the hydrolysis of ATP the protein is anchored into the ER membrane with the N-terminus facing the cytosol
what do hydropathy profiles do
predicts likely topogenic sequences in integral membrane proteins
