http://us.expasy.org/cgi-bin/niceprot.pl?Q804A4

1OVA, 1jti, 1uhg

Mine and Rupa (2003) [1236] identified residues 38-49, 95-102, 191-200, 243-248 and 251-260 as IgE-binding regions using a series of dodecapeptides offset by two amino acids from the previous peptide. The sera were from 18 patients with positive double-blind, placebo-controlled food challenges to egg white.

Elsayed and Stavseng (1994) [1237] used enzyme-digested fragments of ovalbumin and synthetic peptides to identify residues 1-19, 34-46 and 47-55 as allergenic. Honma et al (1996) [1238] identified IgE binding to residues 357-366 using a similar approach.

de Groot J and de Jongh (2003) [1239] show by DSC that thermal denaturation of native ovalbumin occurs at about 75°C in 20 mM phosphate buffer (pH 7.0) but at approximately 85°C if the more stable S-ova form (see below) is used.

Tagaki et al. (2003) [1244] reported that ovalbumin was relatively stable to both simulatated gastric and intestinal fluid and that preheating increased the stability to proteolysis.

Mine and Zhang (2002) [1245] found that ovalbumin retained its IgE binding capacity after denaturation by reduction and carboxymethylation, heat or urea. This suggests that IgE bound to linear epitopes which are thermostable.

Not known.

Ovalbumin functions as a storage protein in egg and is approximately 55% (w/w) of the egg white protein (Burley & Vadehra, 1989) [1258]. Although ovalbumin is a member of the serpin family, native ovalbumin, N-ova, is not a protease inhibitor. The inhibitory serpin central loop forms an alpha-helix (Stein et al. 1991) [1226] and proteolysis does not lead to insertion of this region into the beta-sheet and the dramatic conformation change seen in active serpins (Wright et al. 1990) [1225].

Native ovalbumin has a single solvent accessible disulphide bridge and four reduced cysteines which are buried. It is slowly converted in eggs into two more stable forms, I-ova and S-ova (Smith and Back, 1965) [1228]. I-ova is a reversible inhibitor of cathepsin G, chymotrypsin, bovine pancreatic trypsin, porcine pancreatic elastase and αlpha-lytic proteinase (Mellet et al, 1996) [1227]. S-ovalbumin has a similar fold to native ovalbumin (Yamasaki et al. 2003) [1655]. Conversion of 3 serine residues from L- to D-isomers probably accounts for the stabilization (Takahashi et al. 2005) [1656].

Ovalbumin is also N-glycosylated on asparagine 293 (Glabe et al, 1980 [1233]; Rago et al, 1992 [1235]), N-terminally acetylated (Narita and Ishii, 1962 [1234]) and phosphorylated at serine 68 and/or 344 (Nisbet et al, 1981 [1232]) with an average 1.73 phosphates per molecule (Ekman and Jäger, 1993 [1231]) and thus a dominant diphosphorylated form.

Binding of a T-cell epitope of ovalbumin to the histocompatibility complex has been characterised by Fremont et al. (1995) [1229].

Ovalbumin has been used as an allergen in many animal model studies of allergy (Strid et al. (2004) [1246]; Pilegaard & Madsen, 2004 [1247]).

Anti-ovalbumin IgE is constituitively expressed in a strain of mice created by Matsuoka et al. (1999) [1257] and these have been used by Sato et al. (2003) [1256] and Omata et al. (2005) [1255] as animal models of food allergy.

Ovalbumins from the eggs of other birds have very similar sequences (O73860 from turkey has 90% identical residues while P19104 and Q6V115 from Japanese and common quail have 88% and 87% respectively) and thus are likely to show IgE cross-reactivity. There is a related sequence in chicken P01014 with 57% identity which also might show IgE cross-reactivity.