how does a nuclear localization signal (nls) work? a. an nls sequence is part of the importin protein. this enables importin to bind to proteins destined to be cargo moved from the cytosol into the nucleus. b. an nls sequence is a tag on cargo destined to be moved from the cytosol into the nucleus. c. an nls sequence is part of ran gtpase. this enables ran to bind to and activate importin, thereby allowing importin to move into the nucleus.