Our Science – Ramamurthi Website
Kumaran S. Ramamurthi, Ph.D.
A longstanding challenge in developmental biology is to understand how organisms construct large structures that ultimately help define how that organism looks. We are approaching this problem by examining the morphogenesis of a simple organism, a bacterial spore, and are trying to understand how a spore ends up looking like a spore. When the rod-shaped bacterium Bacillus subtilis faces starvation, it elaborates a spherical internal organelle that will eventually mature into a spore, a dormant cell type that protects the bacterium's genetic material from environmental onslaughts. As the spore matures, the bacterium deposits a thick protein shell, called the spore coat on the surface of the developing spore which will eventually protect the spore when it is released. The spore coat is composed of some seventy different proteins, is the outermost structure of the spore, and is what makes a spore look like a spore.
How is the spore coat assembled?
Assembly of the massive coat depends on a tiny peptide, called VM, which anchors the coat onto the surface of the developing spore. How does the peptide localize to the right place? We have discovered that the convex, or positively curved, membrane surface of the developing spore is a landmark that VM recognizes and that this geometric cue recruits VM to its proper subcellular location. Next, VM recruits another protein, called IVA, which then polymerizes by hydrolyzing ATP to form a stable platform atop which every other coat protein sequentially assembles. Protein sorting driven by a geometric cue, and protein assembly driven by ATP hydrolysis, are novel mechanisms for the assembly of a supramolecular structure. We are now employing genetic, biochemical, cytological, and biophysical approaches to understand the detailed mechanisms of how these early events in coat assembly occur and how the self-assembly of the spore coat proceeds beyond these initial steps.
***Graduate students that are interested in a postdoctoral fellowship are encouraged to send their CV directly to Kumaran Ramamurthi (ramamurthiks[at]mail.nih.gov)***
This page was last updated on 6/7/2013.