The invention provides for polypeptides that bind to Ras proteins and methods of using the same, as described herein. For example, the disclosure provides an isolated polypeptide comprising a fibronectin domain, and a first peptide domain at least 90% identical to an amino acid sequence selected from a group consisting of (SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, and SEQ ID NO: 10), and a second peptide domain at least 90% identical to an amino acid sequence selected from a group consisting of (SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, and SEQ ID NO: 15) that specifically binds to an activated Ras protein.
