Gutheil J C, Mane S, Kapil V, Needleman S W
Department of Medicine, University of Maryland Cancer Center, Baltimore 21201.
Hum Pathol. 1989 Dec;20(12):1176-80. doi: 10.1016/s0046-8177(89)80008-5.
In the process of developing accurate quantitation of the ras protein (p21), we have screened available anti-ras antibodies for their utility in immunoprecipitation. Immunoprecipitation with the anti-ras antibody RAP-5 consistently failed to precipitate p21 present in two different cell lines (HSIC-5 and MCF-7), but did precipitate numerous other proteins present in these cell lines. Specificity in immunoprecipitation could not be achieved by varying the concentration of RAP-5. In addition, immunohistochemical staining of the nuclei of occasional polymorphonuclear leukocytes is seen, further supporting the contention that RAP-5 is binding to proteins other than ras p21. We conclude that while RAP-5 may recognize an epitope present on the ras protein, this epitope also appears to be present on a wide variety of other cellular proteins and, as such, RAP-5 is of no use in the immunoprecipitation of p21.
