Structural highlights
Function
[IMA1_MOUSE] Functions in nuclear protein import as an adapter protein for nuclear receptor KPNB1. Binds specifically and directly to substrates containing either a simple or bipartite NLS motif. Docking of the importin/substrate complex to the nuclear pore complex (NPC) is mediated by KPNB1 through binding to nucleoporin FxFG repeats and the complex is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism. At the nucleoplasmic side of the NPC, Ran binds to importin-beta and the three components separate and importin-alpha and -beta are re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran from importin. The directionality of nuclear import is thought to be conferred by an asymmetric distribution of the GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus.
Publication Abstract from PubMed
HIV-1 has caused 35 million deaths globally, and approximately the same number is currently living with HIV-1. The trans-activator of transcription (Tat) protein of HIV-1 plays an important regulatory function in the virus life cycle, responsible for regulating the reverse transcription of the viral genome RNA. Tat is found in the nucleus of infected cells, but can also invade uninfected neighbouring cells. Regions within Tat responsible for these cellular localisations are overlapping and include a nuclear localisation signal (NLS) spanning 48GRKKRR, and a cell penetrating peptide (CPP) signal spanning 48GRKKRRQRRRAPQN. However, the mechanism by which this NLS/CPP region mediates interaction with the nuclear import receptors remains to be resolved structurally. Here, we establish that the HIV-1 Tat:NLS/CPP is able to form a stable and direct interaction with the classical nuclear import receptor importin-alpha and using x-ray crystallography, we have determined the molecular interface and binding determinants to a resolution of 2.0 A. We show for the first time that the interface is the same as host factors such as Ku70 and Ku80, rather than other virus proteins such as Ebola VP24 that bind on the outer surface of importin-alpha.
Structural Basis for Importin-alpha Binding of the Human Immunodeficiency Virus Tat.,Smith KM, Himiari Z, Tsimbalyuk S, Forwood JK Sci Rep. 2017 May 10;7(1):1650. doi: 10.1038/s41598-017-01853-7. PMID:28490747[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Smith KM, Himiari Z, Tsimbalyuk S, Forwood JK. Structural Basis for Importin-alpha Binding of the Human Immunodeficiency Virus Tat. Sci Rep. 2017 May 10;7(1):1650. doi: 10.1038/s41598-017-01853-7. PMID:28490747 doi:http://dx.doi.org/10.1038/s41598-017-01853-7
