Ras-related protein on chromosome 22 (RRP22) family
RRP22 (Ras-related protein on chromosome 22) subfamily consists of proteins that inhibit cell growth and promote caspase-independent cell death. Unlike most Ras proteins, RRP22 is down-regulated in many human tumor cells due to promoter methylation. RRP22 localizes to the nucleolus in a GTP-dependent manner, suggesting a novel function in modulating transport of nucleolar components. 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. Like most Ras family proteins, RRP22 is farnesylated.