title: Plant 4/1 protein: potential player in intracellular, cell-to-cell and long-distance signaling.
abstract: Originally isolated as a result of its ability to interact with the movement protein of Tomato spotted wilt virus in a yeast two-hybrid system, the 4/1 protein is proving to be an excellent tool for studying intracellular protein trafficking and intercellular communication. Expression of 4/1 in vivo is tightly regulated, first appearing in the veins of the cotyledon and later in the vasculature of the leaf and stem in association with the xylem parenchyma and phloem parenchyma. Structural studies indicate that 4/1 proteins contain as many as five coiled-coil (CC) domains; indeed, the highest level of sequence identity among 4/1 proteins involves their C-terminal CC domains, suggesting that protein-protein interaction is important for biological function. Recent data predict that the tertiary structure of this C-terminal CC domain is strikingly similar to that of yeast protein She2p; furthermore, like She2p, 4/1 protein exhibits RNA-binding activity, and mutational analysis has shown that the C-terminal CC domain is responsible for RNA binding. The 4/1 protein contains a nuclear export signal. Additional microscopy studies involving leptomycin and computer prediction suggest the presence of a nuclear localization signal as well.
authors.affiliation: A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University Moscow, Russia.
authors.forename: Sergey Y
authors.initials: SY
authors.lastname: Morozov
authors.affiliation: Department of Virology, Faculty of Biology, Moscow State University Moscow, Russia.
authors.forename: Svetlana S
authors.initials: SS
authors.lastname: Makarova
authors.affiliation: M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences Moscow, Russia.
authors.forename: Tatyana N
authors.initials: TN
authors.lastname: Erokhina
authors.affiliation: Biosafety in Plant Biotechnology, Julius Kühn Institute - Federal Research Centre for Cultivated Plants Quedlinburg, Germany.
authors.forename: Lilya
authors.initials: L
authors.lastname: Kopertekh
authors.affiliation: Biosafety in Plant Biotechnology, Julius Kühn Institute - Federal Research Centre for Cultivated Plants Quedlinburg, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Schiemann
authors.affiliation: Retired USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Owens
authors.affiliation: A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University Moscow, Russia.
authors.forename: Andrey G
authors.initials: AG
authors.lastname: Solovyev
keywords: RNA binding protein; cell-to-cell transport; intracellular transport; long-distance signaling; phloem transport