If a protein lacks any sorting signal, where will it likely reside?

A protein that lacks any sorting signal will typically reside in the cytosol. This is because the cytosol serves as a default location for proteins that do not have specific signals directing them to other organelles or cellular compartments. Proteins that are synthesized in the cytosol remain there unless they possess particular signals that facilitate their transport to locations such as the mitochondria, nucleus, or the Golgi apparatus.

The Golgi apparatus, mitochondria, and nucleus all require specific sorting signals to ensure proteins are accurately directed to those areas. The Golgi serves as a processing and sorting center for proteins that have been synthesized in the rough endoplasmic reticulum, while the mitochondria and nucleus have unique mechanisms for importing proteins, which are dependent on specific signaling sequences. Thus, without these signals, the protein is most likely to remain in the cytosol where it can function in metabolic processes or be involved in various cellular activities.