What triggers the start and stop transfer sequences in multipass transmembrane proteins?

The start and stop transfer sequences in multipass transmembrane proteins are primarily determined by the presence of hydrophobic and hydrophilic amino acids within the protein's sequence. These sequences are crucial for the proper incorporation of the protein into the lipid bilayer of the membrane.

Hydrophobic amino acids tend to be embedded within the membrane, serving as stop transfer sequences that anchor the protein in place. Conversely, the presence of hydrophilic regions allows for interactions with the aqueous environment, which is necessary for both the initiation and termination of the translocation process. The specific arrangement of these hydrophobic and hydrophilic segments dictates how the protein spans the membrane multiple times, resulting in the finalized structure of the protein.

While other factors such as glycosylation patterns, protein folding states, and membrane lipid composition can influence the overall behavior and functionality of proteins, it is the interaction of the amino acids themselves that directly dictates how and where a protein will be integrated within the membrane.