<Table> <Tr> <Td_colspan="2"> View / Edit Human </Td> <Td_colspan="2"> View / Edit Mouse </Td> </Tr> </Table> <Tr> <Td_colspan="2"> View / Edit Human </Td> <Td_colspan="2"> View / Edit Mouse </Td> </Tr> <P> Tumor protein p53, also known as p53, cellular tumor antigen p53 (UniProt name), phosphoprotein p53, tumor suppressor p53, antigen NY - CO-13, or transformation - related protein 53 (TRP53), is any isoform of a protein encoded by homologous genes in various organisms, such as TP53 (humans) and Trp53 (mice). This homolog (originally thought to be, and often spoken of as, a single protein) is crucial in multicellular organisms, where it prevents cancer formation, thus, functions as a tumor suppressor . As such, p53 has been described as "the guardian of the genome" because of its role in conserving stability by preventing genome mutation . Hence TP53 is classified as a tumor suppressor gene . (Italics are used to denote the TP53 gene name and distinguish it from the protein it encodes .) </P> <P> The name p53 was given in 1979 describing the apparent molecular mass; SDS - PAGE analysis indicates that it is a 53 - kilodalton (kDa) protein . However, the actual mass of the full - length p53 protein (p53α) based on the sum of masses of the amino acid residues is only 43.7 kDa . This difference is due to the high number of proline residues in the protein, which slow its migration on SDS - PAGE, thus making it appear heavier than it actually is . In addition to the full - length protein, the human TP53 gene encodes at least 15 protein isoforms, ranging in size from 3.5 to 43.7 kDa . All these p53 proteins are called the p53 isoforms . The TP53 gene is the most frequently mutated gene (> 50%) in human cancer, indicating that the TP53 gene plays a crucial role in preventing cancer formation . TP53 gene encodes proteins that bind to DNA and regulate gene expression to prevent mutations of the genome . </P>

What is the function of the p53 protein