Peripheral framework of carrot cell nucleus contains a novel protein predicted to exhibit a long alpha-helical domain.
A monoclonal antibody, CML-1, raised against carrot (Daucus carota L.) nuclear-matrix proteins selectively labeled the nuclear periphery of carrot protoplasts when visualized by confocal and electron microscopy. To identify the constituent proteins of higher plant cells structurally homologous to the vertebrate nuclear lamina, we cloned overlapping cDNAs partially encoding a CML-1-recognized protein and determined the entire sequence including the open reading frame. When the deduced amino acid sequence was compared with other known protein sequences contained in major databases, no protein was found to show high sequence identity across the whole region of the protein, while the partial sequence showed strong similarities with myosin, tropomyosin, and some intermediate filament proteins. The protein, designated NMCP1, had an estimated molecular mass of 133.6 kDa and showed three characteristic domains. The central domain contains long alpha-helices exhibiting heptad repeats of apolar residues, demonstrating structural similarity to that of filament-forming proteins. The terminal domains are predominantly nonhelical and contain potential sequence motifs for nuclear localization signals. NMCP1 has many recognition motifs for different types of protein kinases, including cdc2 kinase and PKC. These results suggest that NMCP1 protein forms coiled-coil filaments and is a constituent of the peripheral architecture of the higher plant cell nucleus.
Masuda
K
K
Faculty of Agriculture, Hokkaido University, Sapporo, Japan. kmasuda@res.agr.hokudai.ac.jp
Xu
Z J
ZJ
Takahashi
S
S
Ito
A
A
Ono
M
M
Nomura
K
K
Inoue
M
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018552:Daucus carota / Q000235:genetics* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D015530:Nuclear Matrix / Q000737:chemistry* / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics; D017433:Protein Structure, Secondary; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; C105993:NMCP1 protein, Daucus carota; D009687:Nuclear Proteins; D010940:Plant Proteins