"It appears that different proteins in different pathways are competing for the MAPK enzyme inside these living organisms," said Stanislav Shvartsman, associate professor in the Department of Chemical Engineering and the Lewis-Sigler Institute for Integrative Genomics who earned his Ph.D. from Princeton in 1999. "Since these proteins are fighting for the same limited resource -- the enzyme -- they indirectly control one another, which in turn coordinates the developmental signals."
Conventional biology teaches that enzymes like MAPK act on certain molecules, called substrates, to regulate chemical reactions. The new findings are surprising because it appears that, through competition with one another, the substrates of MAPK are, in fact, influencing the enzyme's activity.
"In a way, it's like the tail wagging the dog," Shvartsman said. "The substrates are regulating the enzyme, and, by extension, mediating the chemical reactions."
Eric Wieschaus, Princeton's Squibb Professor in Molecular Biology who received the 1995 Nobel Prize in medicine for his pioneering work in developmental biology, said, "Their results argue convincingly that these signaling molecules are interacting with each other in a competitive way such that even before anything gets to the DNA, they've already made decisions. Essentially the decisions aren't just made in terms of DNA, but also in terms of proteins working together. This is, in a way, revolutionary."
The research team, led by Princeton chemical engineering graduate student Yoosik Kim, focused its attention on the interaction between MAPK and two proteins involved in two different signaling pathways for head-to-tail pattern formation. The first of these proteins is part of the pathway that governs the development of the head. The second protein plays a significant role in the chemical circuit that controls the development of the ends of the embryo, i
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