You are a secretin, one of 12 identical subunits of a transporter in the outer m
ID: 54660 • Letter: Y
Question
You are a secretin, one of 12 identical subunits of a transporter in the outer membrane. You fold at your destination.
1.) Are you recognized during translation?
-No. -Yes, by SRP. -Yes, by SecA.
2.) Do you bring the ribosome with you to the cytoplasmic membrane?
-No. -Yes.
3.) Which of the following do you require? Select all that apply.
-The insertase. -The ancillary Sec complex. -The Tat translocase. -The Sec translocase.
4.) Is your signal sequence removed?
-Yes. -No. -I don't have one.
!!!!! Please explain your answers!!!!!!
Explanation / Answer
1.) Yes, recognized during translation by SRP.The release of secretin by duodenal acidification is mediated by a secretin releasing peptide (SRP).
2.) No, they do not bring the ribosome with them to the cytoplasmic membrane.Ribosomes are bound to the surface of Rough ER.
3). It requires -The Tat translocase. -The Sec translocase.
Sec-translocase catalyzes the export of newly synthesized proteins with an N-terminal signal sequence in their unfolded state through the combined action of an ATP-dependent motor protein SecA and a membrane embedded protein conducting channel SecYEG. Moreover, the Sec-translocase was also found to catalyze the membrane insertion of most cytoplasmic membrane proteins.In bacteria, secretory proteins cross the cytoplasmic membrane either via the general secretion pathway (Sec-pathway)or the twin arginine translocation (Tat-pathway). These pathways are present in all domains of life, i.e., bacteria, archaea, and eukarya.
4.) Yes, the signal sequence removed.
Secretin is initially synthesized as a 120 amino acid precursor protein known as prosecretin. This precursor contains an N-terminal signal peptide, spacer, secretin itself (residues 28–54), and a 72-amino acid C-terminal peptide.
The mature secretin peptide is a linear peptide hormone, which is composed of 27 amino acids and has a molecular weight of 3055.The signal sequence is removed from the mature peptide.
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