Allergen Data Collection - Update: Cow's Milk (Bos domesticus)
Internet Symposium on Food Allergens 4(1): 19-106 (2002) [http://www.food-allergens.de]
7.2 Properties of alpha-Lactalbumin

7.2.1 Molecular Biological Properties
 
alpha-Lactalbumin (alpha-LA) References
Allergen Nomenclature  Bos d 4 (1) Allergen Nomenclature Sub-Committee 2001
Isoallergens and Variants
Genetic variants A and B (1)
(1) Bell et al. 1970
Molecular Mass
SDS-PAGE: 14.2 kDa (1), 13 kDa  (2)
ESI-MS: 14178 Da (3)
(1) Docena et al. 1996
(2) del Val et al. 1999
(3) Slangen & Visser 1999
Isoelectric Point  pI 4.8
(1) Wal 1998
Amino Acid Sequence, mRNA, and cDNA
alpha-LA  
SWISS-PROT: P00711
GenBank: X06366, M18780, J05147, M90645
PIR: LABO
Amino acids 123 residues (1)
mRNA 703 bp (2), 724 bp (4)
cDNA  
Gene 3090 bp (3), 2044 bp (5)
(1) Brew et al. 1970
(2) Hurley & Schuler 1987
(3) Vilotte et al. 1987
(4) Wang et al. 1989
(5) Bleck & Bremel 1993
recombinant Protein
expression in Escherichia coli:
expression of recombinant alpha-LA (1)

expression in yeasts:
expression of recombinant alpha-LA in Saccharomyces cerevisiae (2)

expression in transgenic mice:
expression of recombinant alpha-LA (3)

(1) Wang et al. 1989
(2) Viaene et al. 1991
(3) Soulier et al. 1994
3D-Structure
X-ray studies of alpha-LA: significance of conformation for action in lactose synthase (1)
3D-structures of alpha-LA compared with beta-LG and lactoferrin (2)
(1) Pike et al. 1996
(2) Sharma et al. 2001
Posttranslational Modifications
Disulfide Bridges:
4 disulfide bonds:  6-120, 28-111, 61-77, 73-91 (2)
Glycosylation:
Carbohydrate composition: GlcNAc, GalNAc, Man, Gal, Fuc, NeuAc (1)
Single glycosylation site: Asn-45 (3)
Detection of a glycosylated isoform (16-kDa in SDS-PAGE) with carbohydrate detection kit (4)
Mixture of 14 different glycosylated isoforms and proposed composition of monosaccharides (15.8 to 16.7 kDa by ESI-MS) (5)
Analysis of carbohydrates released from alpha-LA by mass spectrometry (5)
(1) Barman 1970
(2) Vanaman et al. 1970
(3) Hopper & McKenzie 1973
(4) Kim & Jiminzez-Flores 1994
(5) Slangen & Visser 1999
Biological Function
alpha-LA belongs to the family 22 of glycosyl hydrolases (lysozyme c superfamily), regulatory subunit of lactose synthase (1)
Calcium binding properties (2), 2 Ca2+ binding sites one of which with high affinity (3)
(1) SWISS-PROT
(2) Hiraoka et al. 1980
(3) Kronman et al. 1981
Location
production in mammary gland (1)
(1) SWISS-PROT
Sequence Homology
alpha-LA from water buffalo: aa sequence identity 99% (1)
alpha-LA from goat and sheep: aa sequence identities 95% and 94% (1)
human alpha-LA: aa sequence identity 78% (3)
lysozyme from hen's egg white: alpha-LA evolved from the calcium- binding
lysozyme along the mammalian lineage after the divergence of birds and mammals (2)
lysozyme from various species: aa sequence identity up to 46% (1)
(1) BLAST at PIR
(2) Nitta & Sugai 1989
(3) Wal 1998

7.2.2 Allergenic Properties
 
alpha-Lactalbumin (alpha-LA) References
Frequency of Sensitization
IgE-binding to alpha-LA in 0-80% of patients (1)
(1) see 7.1 Sensitization to Cow's Milk Allergens
B-Cell Epitopes
IgE binding sites located on alpha-LA:
Peptides Positivity
in Patients
Ref.
1-16 (synthetic peptide) 64% (c) (3)
5-18 (synthetic peptide) + (a) (1)
6-10 :S-S: 115-123 (tryptic peptide) 11% (a) (2)
13-26 (synthetic peptide) 45% (c) (3)
17-58 (tryptic peptide) 26% (a) (2)
47-58 (synthetic peptide) 27% (c) (3)
59-94 (reduced tryptic peptide)  16% (a) (2)
59-93 (native tryptic peptide) 26% (a) (2)
93-102 (synthetic peptide) 27% (c) (3)
109-123 (tryptic peptide) 11% (b) (2)

(a) direct ELISA, EAST / RAST
(b) EAST / RAST-inhibition
(c) dot / immunoblot (SPOTs membrane technique)

(1) 2 patients with CMA
(2) 19 patients with CMA
(3) 11 patients with persistent CMA (4-18 years of age, IgE to cow's milk >100 kU(A)/L), positivity of 73% to at least 1 of the 4 IgE-binding epitopes; none of these epitopes detected by sera from 8 children <3 years of age (IgE to cow's milk <30 kU(A)/L) who are likely to outgrow CMA; 3 IgG binding regions identified using 7 sera from patients with persistent CMA (1)

(1) Adams et al. 1991
(2) Maynard et al. 1997
(3) Järvinen et al. 2001
Cross-Reactivity
sequence homology of beta-LG peptide 124-134 and alpha-LA 5-18, both IgE- binding (1)
(1) Adams et al. 1991
PBMC Proliferation
stimulation with  alpha-LA (1)
(1) see Diagnostic Features of CMA: CBMC Proliferation
T-Cell Clone (TCC) Reactivity
CMA in infants with atopic dermatitis associated with production of TH-2 cytokines; number of reactive TCC  to alpha-LA (all TCC CD4+ and expressed alpha/beta T-cell receptor):
TCC reactivity No. of TCC alpha-LA
2 patients with CMA 40 8
2 patients without CMA 36 0
(1) Schade et al. 2000
Alteration of Allergenicity
trypsin hydrolysis:
IgE binding to different tryptic peptides of alpha-LA in 8/19 sera from cow's milk allergic patients  (ELISA) (1)
(1) Maynard et al. 1997

see also 10 Stability of Cow's Milk Allergens

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