What type of sequence is the TM domain for single-pass membrane proteins?

The TM domain for single-pass membrane proteins is accurately described as a start-transfer sequence. This type of sequence is characterized by its ability to initiate the insertion of the polypeptide chain into the membrane. The start-transfer sequence typically consists of a hydrophobic region that serves as a signal for the ribosome to insert the nascent protein into the endoplasmic reticulum membrane during protein synthesis.

In single-pass membrane proteins, this hydrophobic region persists, anchoring the protein within the lipid bilayer after the translation process is complete. The presence of the start-transfer sequence is essential for properly orienting the protein in the membrane and ensuring that any functional domains are located correctly in relation to the cytoplasm and extracellular regions of the cell.

Understanding this function is crucial, as it highlights the role of specific sequences in protein topology and function, particularly in membrane-integrated proteins. The implications of this knowledge extend into various biological processes, including signaling and transport functions carried out by membrane proteins.