The binding protein associates with monomeric phaseolin

• Published in: Plant physiology (Bethesda) Vol. 107; no. 4; pp. 1411 - 1418
• Main Authors: Vitale, A. (Consiglio Nazionale delle Ricerche, Milano, Italy.), Bielli, A, Ceriotti, A
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01-04-1995
• Subjects: ADENOSINE TRIPHOSPHATE; ADENOSINTRIFOSFATO; Antiserum; Binding sites; Biological and medical sciences; Carrier proteins; Cell biochemistry; Cell Biology and Signal Transduction; Cell physiology; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; COTILEDONES; COTYLEDON; Cotyledons; Endoplasmic reticulum; Fundamental and applied biological sciences. Psychology; GLOBULINAS; GLOBULINE; GRAINE; METABOLISME DES PROTEINES; METABOLISMO PROTEICO; Monomers; PHASEOLUS VULGARIS; Plant physiology and development; PROTEINAS; PROTEINAS AGLUTINANTES; PROTEINE; PROTEINE DE LIAISON; Proteins; RETICULO ENDOPLASMATICO; RETICULUM ENDOPLASMIQUE; SEMILLA; Storage proteins; Trimers; Vacuoles; Cotyledon; Enzyme; Cysteine endopeptidases; Glycoproteins; Grain legume; Binding protein; Leguminosae; Legumain; Phaseolus vulgaris; Dicotyledones; Angiospermae; Hydrolases; Spermatophyta; Transport; Proteinases; Endoplasmic reticulum
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.107.4.1411

The association of the binding protein (BiP) with newly synthesized proteins in the endoplasmic reticulum (ER) of developing bean (Phaseolus vulgaris) cotyledonary cells was investigated. ATP-sensitive association with many polypeptides was detected. The fraction of newly synthesized polypeptides associated with BiP varies among different proteins. The relationship between subunit assembly and binding to BiP was investigated in the case of the vacuolar trimeric glycoprotein phaseolin. In spite of the presence of a significant pool of phaseolin trimers in the ER, only monomeric phaseolin is found in association with BiP. On the whole, our results point to a general role of BiP in the synthesis of plant secretory proteins and indicate that, in the case of phaseolin, BiP binding sites are concealed during structural maturation in the ER, either before or upon formation of trimers. Our results also indicate that trimerization does not constitute a rate-limiting step in the transport of phaseolin to the protein storage vacuoles