Glycinin (soybean allergen)

6.6 Properties of Glycinin

6.6.1 Molecular Biological Properties

Glycinin References

Allergen Nomenclature none

Molecular Mass 320-360 kDa
6 subunits: 58-62 kDa
each subunit: acidic polypeptide 31-45 kDa, basic polypetide 18-20 kDa
exception: acidic subunit A5 10 kDa (1) Brooks & Morr 1985

Isoelectric Point acidic subunits pI 4.8-5.5, basic subunits pI 6.5-8.5
estimated values according to (1) and (2)
(1) Staswick et al. 1981
(2) Lei & Reeck 1987

Amino Acid Sequence, cDNA, and mRNA

Glycinin
(subunits) G1 (5)
( A1, BX) G2 (1)
(A2, B1A) G3 (4)
(A2, B1) G4 (3)
(A4, A5, B3) G (2, 5)
(A3, B4)

SWISS-PROT: P04776 P04405 P11828 P02858 P04347

GenBank: M36686 X15122 X15123 X02626 M10962

Amino Acids A1a: 287
BX: 180 A2: 278
B1a: 180 A: 275
B: 180 A4: 257
A5: 97
B3: 185 A3: 320
B4: 172

mRNA
precursor 1743 bp 1899 bp 1786 bp

cDNA
precursor 4617 bp 3573 bp

(1) Staswick et al. 1984a
(2) Fukazawa et al. 1985
(3) Momma et al. 1985
(4) Cho & Nielsen 1989
(5) Nielsen et al. 1989

recombinant Protein
Expression in Escherichia coli:
glycinin (A1aB1b and A2B1a) 57 kDa (1)
glycinin (A1aB1b) with modified functional and nutritional properties (2)
Expression in Yeast:
site-directed mutagenesis of proglycinin (A1a,B1b) (3) (1) Fukazawa et al. 1985
(2) Kim et al. 1990
(3) Katsube et al. 1998

3D-Structure
X-ray studies of recombinant proglycinin (1, 2) (1) Utsumi et al. 1993
(2) Gidamis et al. 1993

Posttranslational Modifications
Disulfide bonds
acidic and basic subunits linked by disulfide bond:
A2 Cys-86 to B1a Cys-7 (1)
Glycosylation:
small glycosylated portion of glycinin (approx. 1%) (2)
glycosylation of site-mutated proglycinin (4)
Phosphorylation:
in vitro phosphorylation of Ser-75 and Ser-117 (3) (1) Staswick et al. 1984b
(2) Lei & Reeck 1987
(3) Fouques et al. 1998
(4) Katsube et al. 1998

Genetic Variants
at least 5 variants (see Amino Acid Sequence) (1) (1) Staswick et al. 1981

Biological Function
Seed storage protein (11S fraction)

6.6.2 Allergenic Properties

Glycinin References

Frequency of Sensitization
IgE-binding to glycinin in 90% of patients (1, 3)
to 11S-fraction (1, 2), acidic- and basic-subunit (a) (2)
to acidic-subunits (A1a, A1b, A2, A3, and A4) (b) (3)
to acidic-subunit (a) (4)
(a) immunoblot
(b) EAST (1) see 6.1 Sensitization to Soybean Allergens
(2) Burks et al. 1988
(3) Djurtoft et al. 1991
(4) Müller et al. 1998

B-Cell Epitopes
IgE-binding region in acidic glycinin G1 (1) (1) Zeece et al. 1999

Allergenic Potencies
higher IgE-binding to acidic-subunit A4 than to A1a, A1b, A2, and A3 (a) (1)
(a) EAST (1) Djurtoft et al. 1991

Alteration of Allergenicity
heat treatment:
soybeans cooked at 100°C for 2h: IgE-binding to stable acidic-subunit (a) (1)
(a) immunoblot (1) Müller et al. 1998

Glycinin	References
*Frequency of Sensitization* IgE-binding to glycinin in 90% of patients (1, 3) to 11S-fraction (1, 2), acidic- and basic-subunit (a) (2) to acidic-subunits (A1a, A1b, A2, A3, and A4) (b) (3) to acidic-subunit (a) (4) (a) immunoblot (b) EAST	(1) see 6.1 Sensitization to Soybean Allergens (2) Burks et al. 1988 (3) Djurtoft et al. 1991 (4) Müller et al. 1998
*B-Cell Epitopes* IgE-binding region in acidic glycinin G1 (1)	(1) Zeece et al. 1999
*Allergenic Potencies* higher IgE-binding to acidic-subunit A4 than to A1a, A1b, A2, and A3 (a) (1) (a) EAST	(1) Djurtoft et al. 1991
*Alteration of Allergenicity* heat treatment: soybeans cooked at 100°C for 2h: IgE-binding to stable acidic-subunit (a) (1) (a) immunoblot	(1) Müller et al. 1998