What happens to proteins that do not have a sorting signal?

Proteins that lack a sorting signal will remain in the cytosol after their synthesis. In the context of protein trafficking, sorting signals are necessary for directing proteins to specific cellular locations, such as the nucleus, mitochondria, or certain organelles. These signals are often composed of short peptide sequences that are recognized by transport machinery within the cell.

When a protein is synthesized in the ribosome in the cytosol and does not possess a signal that indicates a need for relocation, it does not get sorted into any particular organelle or membrane compartment. Instead, it remains within the cytosol where it can perform functions appropriate to its structure and roles, such as metabolic enzymes or components of cytoskeletal structures.

In contrast, proteins with specific sorting signals would be directed to their intended destinations, such as the cell membrane or other organelles, but for proteins without such signals, retention in the cytosol is the default pathway.