The
Corynebacterium diphtheria MdbA enzyme’s thiol-disulfide oxidoreductase fold
is shown as arrows
and two flanking helices in the lower part of the image. Protein
components of the
enzyme’s active site are depicted as spheres. The electrostatic
potentials across
the surface of the molecule are shown as semitransparent features,
with blue and red
shading representing positive and negative potentials, respectively.
(October 20, 2015) Researchers
at the University of Texas, the University of Connecticut, and the U.S.
Department of Energy's (DOE's) Argonne National Laboratory have discovered
structural similarities among bacteria of various types that create the
possibility of using similar approaches to fight the infections they cause.
The research began by studying Actinomyces bacteria, which
commonly cause oral abscesses and gum tissue infections. As it happens, the
most odious species of this type must rely on Actinomyces oris (A. oris)
bacteria to make attachments to mouth tissues. In this way, the researchers
were led to study how A. oris bacteria make their crucial attachments.
Bacteria secrete a wide variety of proteins, which are
large, complex molecules whose ability to recognize and interact with other
molecules depends critically on how they fold to become three-dimensional
structures with active sites. A. oris bacteria attach to bodily cells and other
bacteria by means of two types of protein composites: one type permits the
bacteria to adhere to tooth surfaces, and the other is crucial for forming
biofilms and bacterial colonies on gum tissues. These stubby hair-like proteins
are assembled outside an A. oris bacterium's cell wall using protein pieces
secreted in their unfolded, and therefore useless, state. The purpose of the
research was to learn enough about how the pieces, called pili proteins, fold
upon assembly to formulate antibiotic strategies for disrupting the folding
process.
"These pili are very important for virulence, but they
must be arranged and folded correctly in order for a pathogen to recognize and
interact with a person's bodily cells," said Argonne Distinguished Fellow
Andrzej Joachimiak, who collaborated in the research and is the Director of the
Midwest Center for Structural Genomics and the Structural Biology Center.
"Before we undertook this study, people didn't understand how the proteins
folded when being assembled. This is a completely new discovery."