There is a splice isoform O44119-2 which translates AF034954; AAC48288.1.
3D Structure Accession No.:
N/A
Calculated Masses:
32907 Da
Experimental Masses:
34 kDa (Pan s 1 from Panuliris stimpsoni, Leung et al. 1998 [1555]).
36 kDa (tropomyosin from Panuliris argus, Musmand et al. 1993 [1707]).
38 kDa (tropomyosin from Panuliris homarus, Leung et al. 1996 [1557]).
Oligomeric Masses:
Tropomyosins form dimers.
Allergen epitopes:
Not known for Hom a 1. However, the data on shrimp allergens Pen a 1 and Pen i 1 is 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.
DeWitt et al. (2004) [1536] report that the level of sequence identity of tropomyosins with Pen a 1 is 99% for lobster (Homarus americanus), 92% for crab (Charybdis feriatus), 78-82% for insects and dust mites, 71% for a nematode (Caenorhabditis elegans) and 57% for both blue mussel (Mytilus edulis) and human, suggesting that IgE cross-reactivity is very likely for the invertebrate tropomysosins. DeWitt et al. (2004) [1536] also showed specific IgE binding to recombinant Pen a 1 and seven invertebrate extracts with 9 sera. 6 sera bound extracts from crustacea most strongly, 2 bound dust mite extract more strongly and one serum showed similar binding with both extracts. rPen a 1 bound 94% of the IgE from the 6 crustacea specific sera and gave 50% inhibition of the binding of extracts at about 0.1 µg/ml.
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 Hom a 1 (also rPan s 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.
Native tropomyosin was prepared from Homarus americanus extract was SDS-PAGE as described in immunoblotting.
DeWitt AM, Mattsson L, Lauer I, Reese G, Lidholm J.
Recombinant tropomyosin from Penaeus aztecus (rPen a 1) for measurement of specific immunoglobulin E antibodies relevant in food allergy to crustaceans and other invertebrates.
Mol Nutr Food Res. 48(5):370-379. 2004
PUBMED ID:
15672477
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
Leung PS, Chow WK, Duffey S, Kwan HS, Gershwin ME, Chu KH.
IgE reactivity against a cross-reactive allergen in crustacea and mollusca: evidence for tropomyosin as the common allergen.
J Allergy Clin Immunol. 98(5 Pt 1):954-961.
1996
PUBMED ID:
8939159
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