A new latex allergen classified into the plant defense-related reductase family

Abstract

Rationale As sequence information on genes and proteins is accumulated in databases, it becomes easy to identify a large number of proteins in a short time with proteomics approaches. Application of such techniques to allergenic proteins is referred to allergenomics. In this study, we tried to find unidentified latex allergens with an allergenomics method. Methods Proteins extracted from non-ammoniated rubber latex was two-dimensionally separated according to their isoelectric points (pI) and molecular weights then transferred onto a membrane. IgE-recognizing proteins were visualized by immunoblotting using a pooled serum from latex-allergic people. Spots of the allergenic proteins were cut out form the gel and the allergens were site-specifically in-gel digested by trypsin. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) spectra of the resultant fragments and MS/MS spectra of some prominent peptide-ions were recorded on a TOF-TOF instrument. From these mass-spectrometric data, the allergens were assigned by database searches. Results A few new latex allergens as well as several previously reported allergens such as patatin-like proteins (Hev b 7), enolase (Hev b 9), and havamine were identified with this approach. One of the novel latex allergens (32 kD pI 5.2) was sequentially homologous to plant defense-related reductases like isoflavone reductase and phenylcoumaran benzylic ether reductase. Conclusions We first identified a defense-related reductase as a latex allergen. Several allergens belonging to the plant defense-related reductase family (Bet v 6-related allergens) have already been found from fruits, vegetables, and pollen. Considering the sequence similarities among them, we can predict the cross-reactivity of the defense-related reductase found from natural rubber.