There are about 2-4 million proteins in 1 femtolitre of cytoplasm. These proteins constitute the crucial infrastructure of the cell, performing diverse functions like catalysis (by enzymes), transport (by motor proteins), and signaling. How do these proteins perform these tasks in a streamlined manner in such a crowded environment? The answer to this is regulation. Regulation of activity of these proteins, based on internal or external signals, is crucial for cellular homeostasis. However, there are multiple ways of regulating a protein. For instance, the activity of an enzyme, once expressed in the cell, can be regulated by covalent modification, allosteric regulation or by regulating the half-life of the enzyme. Why one regulatory mode is chosen over the other during evolution is not entirely clear. Knowing the logic of each regulatory mode is crucial to understand how life works. In my talk, I will present a paradoxical mode of enzyme activity regulation that we discovered in B. subtilis. The enzyme of interest GudB, that breaks glutamate, is regulated by binding to another enzyme, GltAB that catalyzes the opposite reaction. I will present kinetic and structural evidence that in the enzyme complex, GudB is inhibited by GltAB binding. Why to regulate an enzyme in such a complex way? It turns out that this complex mode of regulation is an elegant solution for the metabolic requirements of the interior and the peripheral cells of the Bacillus biofilm. Such a regulatory design offers robustness to change in environmental conditions.I will also briefly present other examples of such designs in biology (made of opposing activities) and discuss their utility in synthetic biology. Finally, I will conclude with an evolutionary perspective of the emergence of this complex in the Bacillus species tree and describe our efforts to evolve such an anti-metabolon using directed evolution.
Vijay Jayaraman is a post-doctoral fellow in the laboratory of Prof. Uri Alon at the Weizmann Institute of Science, Israel. Vijay did his B. Pharma from Madras Medical College, Chennai and then M.Tech (Biotechnology) from West Bengal University of Technology, Kolkata, where he was supported by a fellowship from DBT. He joined JNCASR for his Ph.D. in the lab of Prof. Hemalatha Balaram where he worked on structure-function aspects of the Plasmodium enzyme, fumarate hydratase. Following this, he joined Weizmann Institute of Science for his post-doctoral work in the lab of the late Prof. Dan Tawfik where he worked for 3 years before moving to Prof. Uri Alon’s lab. His Ph.D. was supported by CSIR-UGC and his post-doctoral work was funded by the Israel science foundation and the Feinberg graduate school.