Splitting a protein creates a biological AND gate

Ars Technica : Proteins have been used as biological analogues for mechanical and electrical binary switches in the past, but more complicated structures have been restricted by a limited understanding of protein behavior. Now David Shisa and Matthew Bennett of Rice University in Texas have created an AND gate âmdash;a logic structure that has nonzero output only when its two inputs are equal and nonzeroâmdash;by splitting the RNA polymerase enzyme of the T7 bacteriophage virus. RNA polymerase is responsible for translating DNA into RNA. Shisa and Bennett found that T7 RNA polymerase could be split into two pieces and that each of those pieces was encoded by separate genes. They stuck the two RNA polymerase encoding genes together and then attached them to genes that are activated only in the presence of two particular sugars. As a result, functional T7 RNA polymerase could be created only if both sugars are presentâmdash;the equivalent of an AND gate where the sugars are the inputs and the RNA polymerase is the output. The significant aspect is that RNA polymerase is a heavily studied and well-understood enzyme. By attaching the two parts of the RNA polymerase encoding genes to multiple different genes, researchers can now create systems of multiple logic structures.