title: Acidic phosphoprotein complex of the 60S ribosomal subunit of maize seedling roots. Components and changes in response to flooding.
abstract: We determined that ribosomes of seedling roots of maize (Zea mays L.) contain the acidic phosphoproteins (P-proteins) known to form a flexible lateral stalk structure of the 60S subunit of eukaryotic ribosomes. The P-protein stalk, composed of P0, P1, and P2, interacts with elongation factors, mRNA, and tRNA during translation. Acidic proteins of 13 to 15.5 kD were released as a complex from ribosomes with 0.4 M NH4Cl/50% ethanol. Protein and cDNA sequence analysis confirmed that maize ribosomes contain one type of P1, two types of P2, and a fourth and novel P1/P2-type protein. This novel P-protein, designated P3, has the conserved C terminus of P1 and P2. P1, P2, and P3 are similar in deduced mass (11.4-12.2 kD) and isoelectric point (4.1-4.3). A 35.5- to 36-kD acidic protein was released at low levels from ribosomes with 1.0 M NH4Cl/50% ethanol and identified as P0. Labeling of roots with [32P]inorganic phosphate confirmed the in vivo phosphorylation of the P-proteins. Flooding caused dynamic changes in the P-protein complex, which affected the potential of ribosome-associated kinases and casein kinase II to phosphorylate the P-proteins. We discuss possible alterations of the ribosomal P-protein complex and consider that these changes may be involved in the selective translation of mRNA in flooded roots.
authors.affiliation: Department of Botany and Plant Sciences, University of California, Riverside 92521-0124, USA. serres@mail.ucr.edu
authors.forename: J
authors.initials: J
authors.lastname: Bailey-Serres
authors.forename: S
authors.initials: S
authors.lastname: Vangala
authors.forename: K
authors.initials: K
authors.lastname: Szick
authors.forename: C H
authors.initials: CH
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D047390:Casein Kinase II; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D003313:Zea mays / Q000235:genetics / Q000378:metabolism*
chemical_list: D010750:Phosphoproteins; D010940:Plant Proteins; D012269:Ribosomal Proteins; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D010100:Oxygen