Identification of methionine synthase (Sal k 3), as a novel allergen of Salsola kali pollen

Abstract

Salsola kali pollen is a common cause of pollinosis during summer and early fall in desert and semi-desert regions. The aim of this study was the identification and characterization of Sal k 3, a new allergen from S. kali pollen. S. kali pollen extract was fractionated by SDS-PAGE and the allergenic profile was determined by IgE-immunoblotting using twelve S. kali allergic patients. Protein identification was carried out by the means of mass spectrometry. Using degenerated primers, two DNA fragments encoding N- and C-terminal domain of Sal k 3 were amplified by PCR, then cloned into the PTZ57R/T vector and sequenced. The open reading frame of Sal k 3 fragments were subcloned in the pET-32b(+) vector, expressed in E. coli, and purified by Ni2+ affinity chromatography. The IgE-binding capacity of rSal k 3 fragments was then studied by IgE-immunoblotting, inhibition assays, and skin prick tests. A 45-kDa allergen was identified as a fragment of the cobalamin-independent methionine synthase (MetE) by mass spectrometry and was detected in the sera of 8/12 (66.6%) of S. kali allergic patients. Moreover, inhibition assays demonstrated that the purified rSal k 3 fragments were similar to their counterparts in the crude extract. Sal k 3 represents a new allergen of S. kali pollen and seems to be an important allergenic compound in S. kali pollen.

Immunochemical Characterization of Acacia Pollen Allergens and Evaluation of Cross-Reactivity Pattern with the Common Allergenic Pollens

“…It was thus suggested that probable cysteine residues of the pollen proteins may be associated with interchain disulfide bonds. In previous studies, it was demonstrated that some proteins in pollen extract such as methionine synthase of S. kali or A. retroflexus were partially degraded into two fragments with approximate MWs of 45 and 39 kDa [19, 20]. Taken together, these observations suggested that some proteins in Acacia pollen extract are susceptible to degradation as a result of proteolysis or exposure to a reducing condition.…”

A Recombinant Sal k 1 Isoform as an Alternative to the Polymorphic Allergen from <b><i>Salsola kali</i></b> Pollen for Allergy Diagnosis

“…Q8L5K9), methionine synthase Sal k 3 [14], the profilin Sal k 4 [15,16], the Ole e 1-like protein Sal k 5 and the major allergen and S. kali- specific marker Sal k 1, the subject of this study [11]. …”

“…Several allergens from C. album (Che a 1 [12], Che a 2 and Che a 3 [13]) and S. kali [Sal k 1 [11], Sal k 2 (accession No. Q8L5K9), Sal k 3 [14], Sal k 4 [15,16] and Sal k 5 [17]] pollens have been identified (for a review, see [18]). Sal k 1 is the allergenic marker of S. kali pollen able to discriminate between sensitized and nonsensitized patients to this weed [11].…”

Sal k 5, a Member of the Widespread Ole e 1-Like Protein Family, Is a New Allergen of Russian Thistle <b><i>(Salsola kali)</i></b> Pollen

“…Three allergens have been identified and characterized in C. album pollen: Che a 1, a member of the Ole e 1-like protein family, the profilin Che a 2 and the polcalcin Che a 3 [7] . Regarding S. kali allergens, Sal k 1, a pectin methylesterase, has been described as a major allergen and specific marker of S. kali pollen allergy [9], and the minor allergens reported, Sal k 3, a methionine synthase [13] and the profilin Sal k 4 [14,15]. In addition, sera of patients allergic to S. kali contain IgEs able to bind to other proteins in immunoblotting with high frequency, such as 19- or 25-kDa bands that are recognized by a significant number of patients from several Spanish populations.…”