Importin {alpha} from Arabidopsis thaliana is a nuclear import receptor that recognizes three classes of import signals
- Michigan State Univ., East Lansing, MI (United States)
Protein import into the nucleus is a two-step process. In vitro import systems from vertebrate cell extracts have shown that several soluble factors are required. One of these factors is the receptor importin {alpha}, which binds to nuclear localization signals (NLS) in vitro. We previously cloned an importin {alpha} homolog from Arabidopsis thaliana (At-IMP{alpha}) and demonstrated that this protein was not depleted from tobacco (Nicotiana tabacum) protoplasts after permeabilization of the plasma membrane. To determine if At-IMP{alpha} is functional, we used an in vitro NLS-binding assay. We found that At-IMP{alpha} binding is specific, and the receptor is able to recognize three classes of NLS identified in plants. Purified antibodies to At-IMP{alpha} were used to determine the in vivo location of importin a in tobacco protoplasts. Importin a is found in the cytoplasm and nucleus, and it is most highly concentrated at the nuclear envelope. The biochemical properties of nuclear importin {alpha} and localization studies using purified nuclei demonstrate that importin {alpha} is tightly associated with the plant nucleus. Moreover, these results suggest that a fraction of nuclear importin {alpha} interacts with the nuclear pore complex.
- OSTI ID:
- 577267
- Journal Information:
- Plant Physiology (Bethesda), Journal Name: Plant Physiology (Bethesda) Journal Issue: 2 Vol. 114; ISSN 0032-0889; ISSN PLPHAY
- Country of Publication:
- United States
- Language:
- English
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