The unique biosynthetic route from lupinus beta-conglutin gene to blad.
BACKGROUND
During seed germination, beta-conglutin undergoes a major cycle of limited proteolysis in which many of its constituent subunits are processed into a 20 kDa polypeptide termed blad. Blad is the main component of a glycooligomer, accumulating exclusively in the cotyledons of Lupinus species, between days 4 and 12 after the onset of germination.


RESULTS
The sequence of the gene encoding beta-conglutin precursor (1791 nucleotides) is reported. This gene, which shares 44 to 57% similarity and 20 to 37% identity with other vicilin-like protein genes, includes several features in common with these globulins, but also specific hallmarks. Most notable is the presence of an ubiquitin interacting motif (UIM), which possibly links the unique catabolic route of beta-conglutin to the ubiquitin/proteasome proteolytic pathway.


CONCLUSIONS
Blad forms through a unique route from and is a stable intermediary product of its precursor, beta-conglutin, the major Lupinus seed storage protein. It is composed of 173 amino acid residues, is encoded by an intron-containing, internal fragment of the gene that codes for beta-conglutin precursor (nucleotides 394 to 913) and exhibits an isoelectric point of 9.6 and a molecular mass of 20,404.85 Da. Consistent with its role as a storage protein, blad contains an extremely high proportion of the nitrogen-rich amino acids.
Monteiro
Sara
S
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal. smonteiro@isa.utl.pt
Freitas
Regina
R
Rajasekhar
Baru T
BT
Teixeira
Artur R
AR
Ferreira
Ricardo B
RB
D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D017343:Genes, Plant; D018525:Germination; D031297:Lupinus / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics; D055314:Seed Storage Proteins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D010940:Plant Proteins; D055314:Seed Storage Proteins; C042457:conglutin protein, Lupinus angustifolius