Not known for Pan s 1. However, the data on shrimp allergens Pen a 1 and Pen i 1 are likely to be relevant because of cross-reactivity.
Allergen stability: Process, chemical, enzymatic
The allergenicity of crustacea can survive cooking, possibly because tropomyosin have a very simple helical structure which can rapidly refold after denaturation. Extracts from boiled crustacea are frequently used in allergen purification and for extract preparation.
Nature of main cross-reacting proteins:
Leung et al (1998) [1555] reported the cloning of tropomyosins from Homarus americanus, Hom a 1, and Panulirus stimpsoni, Pan s 1. The sequence from Panulirus stimpsoni has 271/274 (98%) residues identical to the splice isoform O44119-2 from Homarus americanus. Leung et al (1998) [1555] reported that binding of IgE from sera from 10/10 crustacean allergic subjects to lobster extracts was inhibited by rMet e 1, rPan s 1 or rHom a 1.
Leung et al (1998) [1554] reported the percentage of amino acid identity of crab Cha f 1 with Met e 1, lobster Pan s 1 and Hom a 1 and Homarus americanus slow muscle, fruit fly and chicken tropomyosins as 90%, 91%, 92%, 96%, 69% and 60% respectively. They found that IgE from the sera from 10/10 crab allergic subjects bound rMet e 1, rPan s 1 and rHom a 1.
Allergen properties & biological function:
Tropomyosins bind to actin in muscle increasing thin filament stability and rigidity. Depolymerization from the pointed end is inhibited, without affecting elongation (Broschat, 1990 [1589]). As tropomyosin prevents the binding of myosin, it may play an important role with troponin in controlling muscle contraction. The sequence exhibits a prominent seven-residues periodicity and this is reflected in the interactions of the 2 polypeptide chains which form a coiled coil structure of two alpha-helices as originally proposed by Crick in 1952 (see the porcine structure 1C1G). Some tropomyosins are N-acetylated modifying the structure of the N terminal region and increasing the affinity for the thin filaments (Greenfield & Fowler, 2002 [1590]).
Allergen purification:
Leung et al (1998) [1555] report the production of recombinant Pan s 1 (also rHom a 1 and rMet e 1) as 60 kDa GST-fusion proteins using the pGEX 1 expression system in E. coli. Only the purification of rPan s 1 is explicitly described starting with a 500 ml culture. Cells were suspended in 5 mls of lysis buffer (1% Triton X-100, 1% Tween-20, 10 mM DTT) and sonicated. The cell debris was demoved by centrifugation at 6000 x g for 15 minutes and the supernatant was added to glutathione agarose (Sigma, St. Louis, MO). After incubation for 2 hours on a rocker, the glutathione agarose was washed 3 times with PBS, pH 7.3, containing 1% Triton X-100 and the bound protein eluted in 2 mls of 5 mM reduced glutathione in 50 mM Tris/HCL, pH 8.0.
Other biochemical information:
References (4)
Broschat KO.
Tropomyosin prevents depolymerization of actin filaments from the pointed end.
J Biol Chem. 265(34):21323-21329. 1990
PUBMED ID:
2250026
Leung PS, Chen YC, Mykles DL, Chow WK, Li CP, Chu KH.
Molecular identification of the lobster muscle protein tropomyosin as a seafood allergen.
Mol Mar Biol Biotechnol. 7(1):12-20. 1998
PUBMED ID:
9597774
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