Domain

Importin-beta, N-terminal domain (IPR001494)

Short name: Importin-beta_N

Domain relationships

None.

Description

This entry represents the N-terminal domain of importin-beta (also known as karyopherins-beta) that is important for the binding of the Ran GTPase protein [PMID: 10367892].

Members of the importin-beta (karyopherin-beta) family can bind and transport cargo by themselves, or can form heterodimers with importin-alpha. As part of a heterodimer, importin-beta mediates interactions with the pore complex, while importin-alpha acts as an adaptor protein to bind the nuclear localisation signal (NLS) on the cargo through the classical NLS import of proteins. Importin-beta is a helicoidal molecule constructed from 19 HEAT repeats. Many nuclear pore proteins contain FG sequence repeats that can bind to HEAT repeats within importins [PMID: 12372823, PMID: 17161424], which is important for importin-beta mediated transport.

Ran GTPase helps to control the unidirectional transfer of cargo. The cytoplasm contains primarily RanGDP and the nucleus RanGTP through the actions of RanGAP and RanGEF, respectively. In the nucleus, RanGTP binds to importin-beta within the importin/cargo complex, causing a conformational change in importin-beta that releases it from importin-alpha-bound cargo. As a result, the N-terminal auto-inhibitory region on importin-alpha is free to loop back and bind to the major NLS-binding site, causing the cargo to be released [PMID: 17170104]. There are additional release factors as well.

GO terms

Biological Process

GO:0006886 intracellular protein transport

Molecular Function

GO:0008536 Ran GTPase binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
Pfam
SMART
PROSITE profiles