Gad c 1 (Allergen M)

Allergen Data Collection - Update: Codfish (Gadus morhua)
Internet Symposium on Food Allergens 2(Suppl.6): 1-18 (2000) [http://www.food-allergens.de]

7.2 Properties of Allergen M (Gad c 1)

7.2.1 Molecular Biological Properties

Allergen M References

Allergen Nomenclature Gad c 1 (1) Larsen & Lowenstein 1999

Molecular Mass
12.328 kDa (calculated) (1)
12-13 kDa (SDS-PAGE) (2) (1) Elsayed & Bennich 1975
(2) Hansen et al. 1996

Isoelectric Point pI 4.75 (1)
(1) Elsayed & Aas 1971

Amino Acid Sequence,mRNA, and cDNA

Gad c 1

SWISS-PROT: P02622

PIR: PVCD

Amino Acids 113 (1)

mRNA

cDNA

(1) Elsayed & Bennich 1975

Genetic Variants / Isoforms
2 IgE-binding precipitates in CRIE (1) (1) Aukrust et al. 1978

Posttranslational Modification
Acetylation:
N-terminal acetylation (1)
Glycosylation:
1 mol Glucose per mol Gad c 1 (2)
Glycosylation site: aa Cys-18 (2)
(1) SWISS-PROT
(2) Elsayed & Bennich 1975

Biological Function
EF-hand calcium binding protein arranged in 3 domains (AB, CD, and EF); domains CD and EF bind 1 Ca2+ ion each; belongs to parvalbumin subfamily, propably involved in muscle relaxation (1, 4)
2 Ca++-binding sites:
site 1: aa 51 and aa 62 (5) on loop aa 49-64 (2)
site 2: aa 90 and 101 (5) on loop aa 88-103 (3) (1) SWISS-PROT
(2) Elsayed et al. 1980
(3) Elsayed et al. 1981
(4) Elsayed & Apold 1983
(5) Permyakov et al. 1987

Sequence Homology
Whole sequence from Allergen M to other paralbumins:
From carp and hake aa 68 and 65 % identity (1)
From frog, turtle, chicken, and rat aa 50-60 % identity (1)
From salmon parvalbumin cDNA clone 24.1 and clone 14.1: aa 58% and 51% identity (2)
Sequence aa 90-102 from Allergen M to IgE- binding epitope 1 from Sj22.6 (allergen from Schistosoma japonicum): (aa 54 % identity,) aa 85 % homology (3) (1) PIR-BLAST
(2) Lindstrøm et al. 1996
(3) Santiago et al. 1998

7.2.2 Allergenic Properties

Allergen M References

Frequency of Sensitization
IgE-binding to Allergen M in 100 % (1) (1) see 5.1 Sensitization to Codfish Allergens

B-Cell Epitopes
IgE-binding regions of Allergen M (5):
aa 13-32 (synthetic peptide) (6)
aa 33-44 (trypsin digest) (1)
aa 49-64 (synthetic peptide) (3)
aa 88-103 (synthetic peptide) (4)
aa 88-108 (trypsin digest), 62 % (a) (2)
aa 88-113 (trypsin digest), 87 % (a) (2)
aa 97-113 (trypsin digest), 15 % (a) (2)
(a) RAST inhibition of IgE- binding to Allergen M
Amino acids critical for IgE-binding
on region aa 49-64: two repetitive sequences (DEDK) and (DELK) spaced by 6 unrelated residues (7)
(1) Elsayed et al. 1976
(2) Elsayed & Apold 1977
(3) Elsayed et al. 1980
(4) Elsayed et al. 1981
(5) Elsayed & Apold 1983
(6) Elsayed et al. 1983
(7) Elsayed et al. 1991

Alteration of Allergenicity
amino acid modification:
acetylation of Tyr-30 decreased allergenic activity, modification of Arg-75 did not (1, 3)
Ca2+ binding:
Unchelating of Ca2+ with EDTA or masking of Arg-75 by cyclohexanedione condensation decreased allergenicity about 25 % (2, 3)
Reduction of IgE- binding to Allergen M after Ca2+- depletion (SDS-PAGE immunoblot) (4)
Oxidation / Deglycosylation:
Significant reduction of IgE- binding to Allergen M after periodate treatment (SDS-PAGE immunoblot) (4)
polymerization:
Polymerization of Allergen M deminished allergenicity (1, 2, 3)
Polymerization of fragment TM 1 (aa 1-75) reduced allergenicity, while polymerization of fragment TM 2 (aa 76-113) to trimer increased its allergenic reactivity (1, 2, 3)
Reduction:
No change in IgE-binding after reduction with 2-mercaptoethanol (SDS-PAGE immunoblot) (4)
(1) Apold & Elsayed 1979
(2) Apold & Elsayed 1980
(3) Elsayed & Apold 1983
(4) Bugajska-Schretter et al. 1998

Allergen M	References
*Frequency of Sensitization* IgE-binding to Allergen M in 100 % (1)	(1) see 5.1 Sensitization to Codfish Allergens
*B-Cell Epitopes* IgE-binding regions of Allergen M (5): aa 13-32 (synthetic peptide) (6) aa 33-44 (trypsin digest) (1) aa 49-64 (synthetic peptide) (3) aa 88-103 (synthetic peptide) (4) aa 88-108 (trypsin digest), 62 % (a) (2) aa 88-113 (trypsin digest), 87 % (a) (2) aa 97-113 (trypsin digest), 15 % (a) (2) (a) RAST inhibition of IgE- binding to Allergen M Amino acids critical for IgE-binding on region aa 49-64: two repetitive sequences (DEDK) and (DELK) spaced by 6 unrelated residues (7)	(1) Elsayed et al. 1976 (2) Elsayed & Apold 1977 (3) Elsayed et al. 1980 (4) Elsayed et al. 1981 (5) Elsayed & Apold 1983 (6) Elsayed et al. 1983 (7) Elsayed et al. 1991
*Alteration of Allergenicity* amino acid modification: acetylation of Tyr-30 decreased allergenic activity, modification of Arg-75 did not (1, 3) Ca2+ binding: Unchelating of Ca2+ with EDTA or masking of Arg-75 by cyclohexanedione condensation decreased allergenicity about 25 % (2, 3) Reduction of IgE- binding to Allergen M after Ca2+- depletion (SDS-PAGE immunoblot) (4) Oxidation / Deglycosylation: Significant reduction of IgE- binding to Allergen M after periodate treatment (SDS-PAGE immunoblot) (4) polymerization: Polymerization of Allergen M deminished allergenicity (1, 2, 3) Polymerization of fragment TM 1 (aa 1-75) reduced allergenicity, while polymerization of fragment TM 2 (aa 76-113) to trimer increased its allergenic reactivity (1, 2, 3) Reduction: No change in IgE-binding after reduction with 2-mercaptoethanol (SDS-PAGE immunoblot) (4)	(1) Apold & Elsayed 1979 (2) Apold & Elsayed 1980 (3) Elsayed & Apold 1983 (4) Bugajska-Schretter et al. 1998