DNA (deoxyribonucleic acid) clamp and DNA. Molecular model of the beta clamp polymerase processivity factor (yellow and pink) from an Escherichia coli bacterium, in complex with a strand of DNA (orange and blue). The clamp is part of a larger molecule (not seen), a DNA polymerase. DNA polymerases are enzymes that synthesise new strands of DNA from a complementary template strand during DNA replication. The clamp directly binds the DNA duplex to keep it bound to the enzyme.