The PBac{HpaI-GFP.A} construct contains an artificial exon (the same as in P{PTT-GA}) that consists of a splice donor site, a multiple tag cassette (Tag:polyHis followed by EGFP without start and stop codons), and a splice acceptor site. The exon is designed to act as a protein trap element when inserted into a coding intron of an endogenous gene in the correct orientation and splice phase.