Which proteins transport proteins containing a nuclear localization signal into the nucleus?

Importins are responsible for the transport of proteins that contain a nuclear localization signal (NLS) into the nucleus. These proteins recognize and bind to the NLS present on cargo proteins, facilitating their transport through the nuclear pore complex. Once inside the nucleus, importins release the cargo, allowing it to carry out its functions within the nuclear environment.

This mechanism is vital for the regulation of various cellular processes, such as gene expression, as many signaling and regulatory proteins need to access the nucleus. The specificity of importins for the NLS ensures that only properly tagged proteins are transported into the nucleus, maintaining cellular order and function.

In contrast, exportins play a role in transporting proteins out of the nucleus, chaperones assist in the proper folding and stabilization of proteins but do not facilitate nuclear transport, and translocons are involved in the translocation of proteins across cellular membranes, such as those of the endoplasmic reticulum. Each of these has distinct functions that do not overlap with the specialized transport of nuclear-localized proteins, highlighting the crucial role of importins in nuclear import processes.