Catalysis
Sometimes, it takes very little to change the course of things. Though frequently it may require the presence of another. Take two people who become lovers and whose destinies change after having met by chance at a friend's house. Or two artists who recognise in each other a similar understanding of things and whose meeting causes something very different to emerge - Georges Braque and Pablo Picasso, Lee Krasner and Jackson Pollock, or Elaine and Willem de Kooning for instance. Or two scientists, for that matter. James Watson and Francis Crick will have no doubt fed on each other's enthusiasm to elucidate the structure of DNA. The same occurs in the world of proteins. It is no secret that proteins frequently work in twos - or indeed threes or more - by binding to one another to perform an overall function. Each individual protein, however, usually has a very distinctive part to play. On more rare occasions, bonding can influence a protein to act differently. This is what happens when two proteins, known as HPF1 and PARP1 (or 2), meet. PARP1/2 is known to act in one way, but when HPF1 binds to it, like two pieces of a jigsaw puzzle that lock to become a different shape, their active sites add up to create a novel one and, in so doing, PARP1/2 behaves differently.
