BD Pharmingen™ Purified Mouse Anti-p21

Cyclins and cyclin-dependent kinases (cdks) are evolutionarily conserved proteins that are essential for cell-cycle control in eukaryotes. Cyclins (regulatory subunits) to form complexes that regulate the progression of the cell cycle. The activity of these complexes is modulated by activating and inhibitory phosphorylation events, as well as by interactions with small regulatory proteins including, p16, p21, p27 and others. These proteins, referred to as inhibitors of Cdk activity (CDkIs) bind to cyclins, cdks or their complexes. p21, also known as senescent cell-derived inhibitor 1 (Sdi1), wild-type p53-activated fragment 1 (Waf1), Cdk-interacting protein 1 (Cip1), and p53-regulated inhibitor of Cdks (Pic1) inhibits cyclin D-cdk4, cyclin E-cdk3, cyclin A-cdk2, and cyclin A-cdk1. p21 can also inhibit cell cycle progression by binding to PCNA and blocking DNA replication. p21 has also shown to be a component of active cyclin-cdk complexes, suggesting that p21-containing complexes may shift between active and inactive states through changes in p21 content. Active, p21-containing complexes appear to contain one p21 molecule, whereas inactive complexes contain multiple p21 molecules. The expression of p21 can be induced in response to number of signals, including transcriptional upregulation by the tumor suppressor protein, p53. Human p21 has a calculated molecular weight of 18 kDa and runs at 21 kDa in SDS-PAGE.

The epitope has been mapped to the last 20 amino acids (residues 145-164) of human p21, one of the most conserved regions between human and mouse p21. Reaction of the antibody with overlapping peptides fragments suggest that the epitope may be further mapped to residues 145-156 (TSMTDFYHSKRR). This sequence overlaps with the sequence of p21 (KRRQTSMTDFYH) which is responsible for the specific interaction of p21 with PCNA.