BBMB Research Seminars

November 1, 2007
Todd Yates
University of California, Los Angeles

"Piecing together the atomic structure of the carboxysome, a primitive bacterial organelle"

1414 Molecular Biology Buidling
4:10 p.m.

Abstract:

Although bacteria lack the traditional membrane- bound organelles associated with eukaryotic cells, they nonetheless benefit from a high degree of internal order. Mechanisms by which bacteria achieve this internal order have become topics of renewed interest. For more than 40 years it has been known that some bacteria contain large, proteinaceous microcompartments resembling viral capsids. The prototypical bacterial microcompartment is the carboxysome, which is present in cyanobacteria and many chemo-autotrophs. The carboxysome enhances carbon dioxide fixation in those microbes by encapsulating all the cell's RuBisCO, along with carbonic anhydrase, thereby providing CO2 at high concentration where RuBisCO is also concentrated. The outer shell of the carboxysome and related microcompartments is composed of several thousand copies of a few distinct protein subunits. The shell appears to restrict the flow of metabolites (e.g. bicarbonate and 3 and 5 carbon sugars) into and out of the carboxysome. Structural studies are beginning to reveal the architectural principles and biochemical mechanisms that underlie bacterial microcompartment function. Progress in elucidating the structure of the carboxysome, as well as components of the related propane diol utilization (pdu) shell from Salmonella, will be discussed.