Structural and functional studies of p21 ras proteins. The products of ras genes have essential cellular functions, but nothing is known about their specific functional role and related structural details. We addressed those questions with a combination of approaches: 1) Monoclonal antibodies against p21 proteins. We developed a panel of monoclonal antibodies recognizing every domain of the protein. Correlating the epitope recognized with the effect of each Mab on the biochemical properties of p21 we constructed a functional map of the protein. Also, by using a selected Mab from our panel we identified a related antigen located in mitochondria this may be a useful approach to identifying yet unknown members of the ras gene family. 2) Radiation inactivation of p21 ras proteins. By means of radiation inactivation techniques we determined that the structure of p21 is homooligomeric; this structure clearly differentiates ras proteins from classical G proteins and offers the basis for a model of biochemical action. We propose that activation of p21 involves subunit reorientation within the oligomer upon binding of guanine nucleotides. 3) Signal transduction through the PI pathway. We studied normal and transformed NIH/3T3 cells to assess the effect of ras and other oncogenes in the process of signal transduction. We showed that there are specific alterations in the phosphoinositide pathway in ras transformed cells, but similar changes are produced by many other oncogenes. A specific stimulation of phospholipase A2-type pathway were observed in all transformed cells studied. These findings are inconsistent with any direct role of p21 proteins as regulatory elements of enzymes of the PI pathway.
