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A Ras homolog member I (ARHI) ARHI (A Ras homolog member I) is a member of the Ras family with several unique structural and functional properties. ARHI is expressed in normal human ovarian and breast tissue, but its expression is decreased or eliminated in breast and ovarian cancer. ARHI contains an N-terminal extension of 34 residues (human) that is required to retain its tumor suppressive activity. Unlike most other Ras family members, ARHI is maintained in the constitutively active (GTP-bound) state in resting cells and has modest GTPase activity. ARHI inhibits STAT3 (signal transducers and activators of transcription 3), a latent transcription factor whose abnormal activation plays a critical role in oncogenesis. Most Ras proteins contain a lipid modification site at the C-terminus, with a typical sequence motif CaaX, where a = an aliphatic amino acid and X = any amino acid. Lipid binding is essential for membrane attachment, a key feature of most Ras proteins. Due to the presence of truncated sequences in this CD, the lipid modification site is not available for annotation. |
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