Cloning and characterization of the group 5 allergens from Dermatophagoides farinae
Objective To obtain the gene coding for the group 5 allergens from Dermatophagoides farinae ( Derf5 ) and predict its molecular characteristics. Methods The total RNA of D. farinae were extracted, and the gene Derf5 was amplified by RT-PCR with the primers designed according to previous sequence published in GenBank. The target gene was linked into pMD19-T Simple plasmid, sequenced and analyzed by bioinformatics software. Results The sequence homology reached to 97.8% between our sequenced result with one complete open reading fragment (ORF) and the reference. The gene encode an extracellular hydrophobic protein with 132 amino acid resides, one signal peptide from 1 to 19 position and one transmembrane domain from 1 to 19 position. The secondary structure was composed of extended strand (1. 52% ), random coil (7.58%) and alpha helix (90.91%). The encoded protein was deduced to have two Casein kinase Ⅱ phosphorylation sites. The similarity of the amino acid sequence of the group 5 allergens were 78% between D. farinae and D. pteronyssinus. Conclusion The gene Derf5 was cloned successfully, and its characteristics was primarily predicted. 
 
Key words: 
Dermatophagoides farinae;  Allergen;  Bioinformatics;  Structure;  Function