Zeolin. A new recombinant storage protein constructed using maize gamma-zein and bean phaseolin.
The major seed storage proteins of maize (Zea mays) and bean (Phaseolus vulgaris), zein and phaseolin, accumulate in the endoplasmic reticulum (ER) and in storage vacuoles, respectively. We show here that a chimeric protein composed of phaseolin and 89 amino acids of gamma-zein, including the repeated and the Pro-rich domains, maintains the main characteristics of wild-type gamma-zein: It is insoluble unless its disulfide bonds are reduced and forms ER-located protein bodies. Unlike wild-type phaseolin, the protein, which we called zeolin, accumulates to very high amounts in leaves of transgenic tobacco (Nicotiana tabacum). A relevant proportion of the ER chaperone BiP is associated with zeolin protein bodies in an ATP-sensitive fashion. Pulse-chase labeling confirms the high affinity of BiP to insoluble zeolin but indicates that, unlike structurally defective proteins that also extensively interact with BiP, zeolin is highly stable. We conclude that the gamma-zein portion is sufficient to induce the formation of protein bodies also when fused to another protein. Because the storage proteins of cereals and legumes nutritionally complement each other, zeolin can be used as a starting point to produce nutritionally balanced and highly stable chimeric storage proteins.
Mainieri
Davide
D
Istituto di Biologia e Biotecnologia Agraria, Consiglio Nazionale delle Ricerche, 20133 Milano, Italy.
Rossi
Marika
M
Archinti
Marco
M
Bellucci
Michele
M
De Marchis
Francesca
F
Vavassori
Stefano
S
Pompa
Andrea
A
Arcioni
Sergio
S
Vitale
Alessandro
A
D000595:Amino Acid Sequence; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism; D027805:Phaseolus; D010940:Plant Proteins / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D012639:Seeds / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D003313:Zea mays; D015028:Zein / Q000378:metabolism*
D046912:Multiprotein Complexes; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C048826:phaseolin protein, Phaseolus vulgaris; D015028:Zein