Our results suggested that the mAbs DA041, DD015, and BE073 were reactive for both immunofluorescence and immunoblotting. Therefore, these mAbs likely recognized linear epitopes in the IRAS protein. In addition, the 3 mAbs were capable of recognition of native full-length IRAS proteins by immunoprecipitation. However, the mAbs BA022 and AH021 specifically recognized bacterially expressed IRAS immunogens and did not detect recombinant IRAS in mammalian cells. This could be related to the different IRAS folding patterns, since misfolded IRAS proteins could result in the exposure of unique immunogenic epitopes different from native proteins. The mAbs BA022 and AH021 could be used as backup reagents to safeguard against antibodyspecific artifacts. In addition, analyzing the overall homology of the amino acid sequence of the PX domain, Sorting Nexins 13 (SNX13) is the most relative protein to IRAS [31] . We found monoclonal antibody DA041 against hIRAS could not react with SNX13 by immunofluorescence assay (data not shown). It was proposed that these antibodies developed here were specific to the PX domain of IRAS.