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Identification of tropomyosin as major allergen of white squid (Loligo edulis) by two-dimensional immunoblotting and mass spectrometry

Yadzir ZH, Misnan R, Murad S

Southeast Asian J. Trop. Med. Public Health, 2012 Jan;43(1):185-91.
PMID: 23082569

IgE-mediated allergic reaction to squid is one of the most frequent molluscan shellfish allergies. Previously, we have detected a 36 kDa protein as the major allergen of Loligo edulis (white squid) by immunoblotting using sera from patients with squid allergy. The aim of this present study was to further identify this major allergen using a proteomics approach. The major allergen was identified by a combination of two-dimensional electrophoresis (2-DE), immunoblotting, mass spectrometry and bioinformatics tools. The 2-DE gel fractionated the cooked white squid proteins to more than 50 different protein spots between 10 to 38 kDa and isoelectric point (pI) from 3.0 to 10.0. A highly reactive protein spot of a molecular mass of 36 kDa and pI of 4.55 was observed in all of the patients' serum samples tested. Mass spectrometry analysis led to identification of this allergen as tropomyosin. This finding can contribute to advancement in component-based diagnosis, management of squid allergic patients, to the development of immunotherapy and to the standardization of allergenic test products as tools in molecular allergology.

Matched MeSH terms: Tropomyosin/immunology*
Molecular and allergenic characterization of recombinant tropomyosin from mud crab Scylla olivacea

Azemi NFH, Misnan R, Keong BP, Mokhtar M, Kamaruddin N, Fah WC, et al.

Mol Biol Rep, 2021 Oct;48(10):6709-6718.
PMID: 34427887 DOI: 10.1007/s11033-021-06661-x

BACKGROUND: Tropomyosin is a major allergen in crustaceans, including mud crab species, but its molecular and allergenic properties in Scylla olivacea are not well known. Thus, this study aimed to produce the recombinant tropomyosin protein from S. olivacea and subsequently investigate its IgE reactivity.
METHODS AND RESULTS: The tropomyosin gene was cloned and expressed in the Escherichia coli system, followed by SDS-PAGE and immunoblotting test to identify the allergenic potential of the recombinant protein. The 855-base pair of tropomyosin gene produced was found to be 99.18% homologous to Scylla serrata. Its 284 amino acids matched the tropomyosin of crustaceans, arachnids, insects, and Klebsiella pneumoniae, ranging from 79.03 to 95.77%. The tropomyosin contained 89.44% alpha-helix folding with a tertiary structure of two-chain alpha-helical coiled-coil structures comprising a homodimer heptad chain. IPTG-induced histidine tagged-recombinant tropomyosin was purified at the size of 42 kDa and confirmed as tropomyosin using anti-tropomyosin monoclonal antibodies. The IgE binding of recombinant tropomyosin protein was reactive in 90.9% (20/22) of the sera from crab-allergic patients.
CONCLUSIONS: This study has successfully produced an allergenic recombinant tropomyosin from S. olivacea. This recombinant tropomyosin may be used as a specific allergen for the diagnosis of allergy.

Matched MeSH terms: Tropomyosin/immunology*
Identification of the major allergens of Charybdis feriatus (red crab) and its cross-reactivity with Portunus pelagicus (blue crab)

Misnan R, Murad S, Yadzir ZH, Abdullah N

Asian Pac J Allergy Immunol, 2012 Dec;30(4):285-93.
PMID: 23393908

Tropomyosin and arginine kinase have been identified as the major allergens in multiple species of crab. Charybdis feriatus is an important commercial crab in this country.

Matched MeSH terms: Tropomyosin/immunology*
Fulltext Identification of tropomyosin and arginine kinase as major allergens of Portunus pelagicus (blue swimming crab)

Rosmilah M, Shahnaz M, Zailatul HM, Noormalin A, Normilah I

Trop Biomed, 2012 Sep;29(3):467-78.
PMID: 23018510

Crab is an important source of food allergen. Tropomyosin represents the main crab allergen and is responsible for IgE cross-reactivity between various species of crustaceans. Recently, other new crab allergens including arginine kinase have been identified. However, information on allergens of the local Portunidcrab is not available. Thus, the aim of this study was to identify the major allergens of Portunus pelagicus (blue swimming crab) using the allergenomics approach. Raw and cooked extracts of the crab were prepared from the crab meat. Protein profile and IgE binding pattern were demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting using sera from 30 patients with crab allergy. The major allergens of the crab were then identified by two-dimensional electrophoresis (2-DE), followed by mass spectrometry analysis of the peptide digests. The SDS-PAGE of raw extract revealed approximately 20 protein fractions over a wide molecular weight range, while cooked extract demonstrated fewer protein bands. The raw extract also demonstrated a higher number of IgE reactive bands than the cooked extract. A heat-resistant protein of 36 kDa has been identified as the major allergen in both raw and cooked extracts. In addition, a heat-sensitive protein of 41 kDa was also recognized as a major allergen in raw crab. The 2-DE gel profile of the raw extract demonstrated about >100 distinct proteins spots and immunoblotting of the 2-DE profile demonstrated at least 12 different major IgE reactive spots with molecular masses between 13 to 250 kDa and isoelectric point (pI) values ranging from 4.0 to 7.0. The 36 and 41 kDa proteins were identified as the crab tropomyosin and arginine kinase, respectively by mass spectrometry. Therefore, this study confirmed that tropomyosin and arginine kinase are the major allergens of the local Portunid crab, P. pelagicus.

Matched MeSH terms: Tropomyosin/immunology*
Fulltext Malaysian cockle (Anadara granosa) allergy: Identification of IgE-binding proteins and effects of different cooking methods

Zailatul HM, Rosmilah M, Faizal B, Noormalin A, Shahnaz M

Trop Biomed, 2015 Jun;32(2):323-34.
PMID: 26691261 MyJurnal

The purpose of this study was to evaluate the effect of different cooking methods on the allergenicity of cockle and to identify proteins most frequently bound by IgE antibodies using a proteomics approach. Raw, boiled, fried and roasted extracts of the cockle were prepared. The protein profiles of the extracts were obtained by separation using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and 2-dimensional gel electrophoresis (2-DE). IgE-immunoblotting was then performed with the use of individual sera from patients with cockle allergy and the major IgE-binding proteins were analyzed by mass-spectrometry. SDS-PAGE of raw extract showed 13 protein bands. Smaller numbers of protein bands were detected in the boiled, fried and roasted extracts. The 2-DE gel profile of the raw extract further separated the protein bands to ~50 protein spots with molecular masses between 13 to 180 kDa and isoelectric point (pI) values ranging from 3 to 10. Immunoblotting of raw extract exhibited 11 IgE-binding proteins with two proteins of 36 and 40 kDa as the major IgE-binding proteins, while the boiled extract revealed 3 IgE-binding proteins. Fried and roasted extracts only showed a single IgE-binding protein at 36 kDa. 2-DE immunoblotting of raw extract demonstrated 5 to 20 IgE reactive spots. Mass spectrometry analysis led to identification of 2 important allergens, tropomyosin (36 kDa) and arginine kinase (40 kDa). Heated extracts showed a reduction in the number of IgE-reactive bands compared with raw extract, which suggest that thermal treatment can be used as a tool in attempting to reduce cockle allergenicity. The degree of allergenicity of cockle was demonstrated in the order raw > boiled > fried ≈ roasted. Two important allergens reacting with more than 50% of patients' sera identified using mass spectrometric approaches were tropomyosin and arginine kinase. Thus, allergens found in this study would help in component based diagnosis, management of cockle allergic patients and to the standardisation of allergenic test products as tools in molecular allergology.

Matched MeSH terms: Tropomyosin/immunology