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PMID: 9193081 Published · ppublish English Journal Article Research Support, U.S. Gov't, Non-P.H.S.

Importin alpha from Arabidopsis thaliana is a nuclear import receptor that recognizes three classes of import signals.

Plant physiology ·Vol. 114 ·No. 2 ·1997-06-00 ·Pages 411-7

Smith HM, Hicks GR, Raikhel NV

Abstract

Protein import into the nucleus is a two-step process. In vitro import systems from vertebrate cell extracts have shown 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, (Hicks et al., 1996). To determine if At-IMP alpha is functional, we used an in vitro NLS-binding assay. We found that At-IMP alpha 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 alpha in tobacco protoplasts. Importin alpha 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.

MeSH Terms
Amino Acid Sequence Arabidopsis/metabolism Biological Transport Cell Compartmentation Cell Nucleus/chemistry,metabolism Molecular Sequence Data Nuclear Envelope/chemistry Nuclear Proteins/isolation & purification,metabolism Plant Proteins/metabolism Plants, Toxic Protein Binding Protein Sorting Signals/metabolism Receptors, Cytoplasmic and Nuclear/metabolism Tobacco/metabolism alpha Karyopherins
Chemicals
Nuclear Proteins Plant Proteins Protein Sorting Signals Receptors, Cytoplasmic and Nuclear alpha Karyopherins
Authors & Affiliations
3 authors, click to expand affiliations / ORCID
Smith H M
Michigan State University-Department of Energy Plant Research Laboratory, East Lansing 48824-1312, USA.
Hicks G R
Raikhel N V
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Article Info
Journal
Plant physiology
Abbr.
Plant Physiol
ISSN
0032-0889
DOI
10.1104/pp.114.2.411
Published
1997-06-00
Pages
411-7
Language
English
Region
United States
NLM ID
0401224
PMCID
PMC158320
Subset
IM
Databases
GENBANK
AF077528
External Links
PubMed source DOI: 10.1104/pp.114.2.411 PMC Full Text View journal details
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