Abstract
Nuclear import of conventional nuclear localization sequence (NLS)- containing proteins initially involves recognition by the importin (IMP) α/β heterodimer, where IMPα binds the NLS and IMPβ targets the IMPα/NLS- containing protein complex to the nuclear pore. Here we examine IMPα from the plant Arabidopsis thaliana (At-IMPα), which exhibits nuclear envelope localization typical of IMPβ rather than IMPα in other eukaryotic cell systems. We show that At-IMPα recognizes conventional NLSs of two different types with high affinity (K(d) of 5-10 nM), in contrast to mouse IMPα (mIMPα), which exhibits much lower affinity (K(d) of 50-70 nM) and only achieves high affinity in the presence of m-IMPβ. Unlike m-IMPα, At-IMPα is thus a high affinity NLS receptor in the absence of IMPβ. Interestingly, At-IMPα was also able to bind with high affinity to NLSs recognized specifically by m-IMPβ and not m-IMPα, including that of the maize transcription factor Opaque-2. Reconstitution of nuclear import in vitro indicated that in the absence of exogenous IMPβ subunit but dependent on RanGDP and NTF2, At-IMPα was able to mediate nuclear accumulation to levels comparable with those mediated by m-IMPα/β. Neither m-IMPα nor -β was able to mediate nuclear import in the absence of the other subunit. At- IMPα's novel NLS recognition and nuclear transport properties imply that plants may possess an IMPα-mediated nuclear import pathway independent of IMPβ in addition to that mediated by IMPα/β.
| Original language | English |
|---|---|
| Pages (from-to) | 22610-22617 |
| Number of pages | 8 |
| Journal | Journal of Biological Chemistry |
| Volume | 274 |
| Issue number | 32 |
| DOIs | |
| Publication status | Published - Aug 6 1999 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Biochemistry
Cite this
Plant importin α binds nuclear localization sequences with high affinity and can mediate nuclear import independent of importin β. / Hübner, Stefan; Smith, Harley M S; Hu, Wei; Chan, Chee Kai; Rihs, Hans Peter; Paschal, Bryce M.; Raikhel, Natasha V.; Jans, David A.
In: Journal of Biological Chemistry, Vol. 274, No. 32, 06.08.1999, p. 22610-22617.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Plant importin α binds nuclear localization sequences with high affinity and can mediate nuclear import independent of importin β
AU - Hübner, Stefan
AU - Smith, Harley M S
AU - Hu, Wei
AU - Chan, Chee Kai
AU - Rihs, Hans Peter
AU - Paschal, Bryce M.
AU - Raikhel, Natasha V.
AU - Jans, David A.
PY - 1999/8/6
Y1 - 1999/8/6
N2 - Nuclear import of conventional nuclear localization sequence (NLS)- containing proteins initially involves recognition by the importin (IMP) α/β heterodimer, where IMPα binds the NLS and IMPβ targets the IMPα/NLS- containing protein complex to the nuclear pore. Here we examine IMPα from the plant Arabidopsis thaliana (At-IMPα), which exhibits nuclear envelope localization typical of IMPβ rather than IMPα in other eukaryotic cell systems. We show that At-IMPα recognizes conventional NLSs of two different types with high affinity (K(d) of 5-10 nM), in contrast to mouse IMPα (mIMPα), which exhibits much lower affinity (K(d) of 50-70 nM) and only achieves high affinity in the presence of m-IMPβ. Unlike m-IMPα, At-IMPα is thus a high affinity NLS receptor in the absence of IMPβ. Interestingly, At-IMPα was also able to bind with high affinity to NLSs recognized specifically by m-IMPβ and not m-IMPα, including that of the maize transcription factor Opaque-2. Reconstitution of nuclear import in vitro indicated that in the absence of exogenous IMPβ subunit but dependent on RanGDP and NTF2, At-IMPα was able to mediate nuclear accumulation to levels comparable with those mediated by m-IMPα/β. Neither m-IMPα nor -β was able to mediate nuclear import in the absence of the other subunit. At- IMPα's novel NLS recognition and nuclear transport properties imply that plants may possess an IMPα-mediated nuclear import pathway independent of IMPβ in addition to that mediated by IMPα/β.
AB - Nuclear import of conventional nuclear localization sequence (NLS)- containing proteins initially involves recognition by the importin (IMP) α/β heterodimer, where IMPα binds the NLS and IMPβ targets the IMPα/NLS- containing protein complex to the nuclear pore. Here we examine IMPα from the plant Arabidopsis thaliana (At-IMPα), which exhibits nuclear envelope localization typical of IMPβ rather than IMPα in other eukaryotic cell systems. We show that At-IMPα recognizes conventional NLSs of two different types with high affinity (K(d) of 5-10 nM), in contrast to mouse IMPα (mIMPα), which exhibits much lower affinity (K(d) of 50-70 nM) and only achieves high affinity in the presence of m-IMPβ. Unlike m-IMPα, At-IMPα is thus a high affinity NLS receptor in the absence of IMPβ. Interestingly, At-IMPα was also able to bind with high affinity to NLSs recognized specifically by m-IMPβ and not m-IMPα, including that of the maize transcription factor Opaque-2. Reconstitution of nuclear import in vitro indicated that in the absence of exogenous IMPβ subunit but dependent on RanGDP and NTF2, At-IMPα was able to mediate nuclear accumulation to levels comparable with those mediated by m-IMPα/β. Neither m-IMPα nor -β was able to mediate nuclear import in the absence of the other subunit. At- IMPα's novel NLS recognition and nuclear transport properties imply that plants may possess an IMPα-mediated nuclear import pathway independent of IMPβ in addition to that mediated by IMPα/β.
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UR - http://www.scopus.com/inward/citedby.url?scp=17744401671&partnerID=8YFLogxK
U2 - 10.1074/jbc.274.32.22610
DO - 10.1074/jbc.274.32.22610
M3 - Article
VL - 274
SP - 22610
EP - 22617
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 32
ER -