Structure and Function of Cell’s Protein-Synthesizing “Machine”

The Agrawal Laboratory is engaged in studies of the mechanism of protein-synthesis, or gene translation, in humans and in pathogenic bacteria. Ribosomes, which lie at the center of the protein synthesis machinery, conduct protein synthesis in all organisms. While the bacterial ribosomes are the major targets of antibiotics, defects in human mitochondrial ribosomes (mitoribosomes) and translation cause multiple devastating genetic diseases. Ribosomes interact with messenger RNA (mRNA), transfer RNAs, and number of protein factors, to facilitate translation. A deep understanding of ribosome structure and function in humans and pathogenic bacteria is necessary for designing or identifying drug targets so that safer drugs can be designed without affecting the human translational machinery. The Agrawal Laboratory’s emphasis is on (i) human mitochondrial, and (ii) mycobacterial ribosomes. His lab uses biochemical, molecular biology, and high-resolution cryo-electron microscopy_[1] (cryo-EM) techniques to study these biological systems.

Human mitochondrial ribosomes (mitoribosomes) synthesize specific sets of proteins required by the eukaryotic cell, including components of protein complexes, crucial for generating ~90% of energy (ATP) for the cell. These ribosomes possess a number of novel features. For example, most mammalian mitochondrial mRNAs are leaderless, i.e., they do not possess either the Shine-Dalgarno sequence or the 5’ cap that guide the recruitment of mRNAs to cytoplasmic ribosomes. In addition, most of the ribosome-binding mitochondrial translational factors possess unique amino-acid segments. The goal of studies in the Agrawal Laboratory includes the elucidation of mechanisms by which (i) leaderless mRNAs are recruited to the ribosomes, and (ii) unique component ribosomal proteins and translational factors participate in the process of mitochondrial protein synthesis. His lab was first do determine the structure of a mammalian mitochondrial ribosome.

To study mycobacterial protein synthesis, the Agrawal Laboratory collaborates with other Wadsworth investigators, including Drs. Keith Derbyshire, Todd Gray, Joseph Wade, Anil Ojha and Pallavi Ghosh. In collaboration with the Ojha Laboratory, his lab was first to determine structure of an alternative form of mycobacterial ribosome, revealing unique features of mycobacterial ribosome hibernation that has implications in mycobacterial dormancy and drug resistance.

Studies in the Agrawal Laboratory allow him to track conformational transitions undergone by the ribosome and its ligands during protein synthesis. Knowledge of specific conformational transitions is key to understanding the molecular mechanisms of protein synthesis itself, as well as the actions of antibiotics that target the bacterial ribosome or ribosomal ligands to inhibit such transitions. Comparison of results obtained for the bacterial ribosome complexes with those for the host cytosolic and mitochondrial ribosome complexes provides useful information that can lead to identification of new drug targets.

Learn more at the 3D Electron Microscopy Group_[2] pages.