7.2 Properties of alpha-Lactalbumin

7.2.1 Molecular Biological Properties
 

alpha-Lactalbumin (alpha-LA)	References
Allergen Nomenclature  Bos d 5	(1) Larsen & Lowenstein 1999
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)	(1) Pike et al. 1996
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. 5-18 (synthetic peptide) + (a) (1) 6-10 :S-S: 115-123 (tryptic peptide) 11% (a) (2) 17-58 (tryptic peptide) 26% (a) (2) 59-94 (reduced tryptic peptide)  16% (a) (2) 59-93 (native tryptic peptide)  26% (a) (2) 109-123 (tryptic peptide) 11% (b) (2) (a) direct ELISA, EAST / RAST (b) EAST / RAST-inhibition (1) 2 patients with CMA (2) 19 patients with CMA	(1) Adams et al. 1991 (2) Maynard et al. 1997
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
Alteration of Allergenicity trypsin hydrolysis: IgE binding to different tryptic peptides of a-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