Page 16 - Abacoa Community News - July '19

Page 16, Abacoa
scieNce oN the cUttiNG edGe

The Scripps Research Institute News

Discovery Of Bacteria’s one that functioned outside the cell, helping attach the common ancestor already carried out this task.”

In addition to lead author Joazeiro, the authors of
Protein Quality Control Agent microbes to hosts. the study, “Alanine Tails Signal Proteolysis in Bacterial
“We have found this is not the complete story,”

Offers Insight Into Origins Of Joazeiro says. “Rqc2 plays a more fundamental role inside Ribosome-Associated Quality Control,” were Tina
of bacterial cells.”
Mueller, George Tsaprailis and Christina Chiang of
Life The next step will be to find out whether the defective Scripps Research in Jupiter, Fla.; Iryna Lytvyenko, Helge
virulence of strep varieties lacking Rqc2 is primarily a Paternoga, Anna Thrun and Simon Anders of Heidelberg
Our cells’ process for consequence of their failure to recycle protein fragments University in Germany; Annika Balke and Christian
transforming genes into inside the cell. As increasing varieties of pathogens Spahn of the Institute of Medical Physics and Biophysics
useful proteins works develop multi-drug resistance to antibiotics, understanding in Berlin, Germany; Katja Nagler and Ilka Bischofs of
much like an automobile bacterial virulence may prove especially necessary. Heidelberg University and the Max Planck Institute for
factory’s assembly line; Equally important to Joazeiro is the realization that Terrestrial Microbiology in Marburg, Germany; and
there are schematics, parts, Rqc2 serves as a “living” molecular fossil, illuminating Julie Maupin-Furlow of the University of Florida in
workers, motors, quality new insights about the ancient ancestral organism that Gainesville, Fla.
control systems and even emerged some four billion years ago to form the very The research was supported by the National
recycling crews. If the base of the tree of life that evolved into the planet’s Institutes of Health (NS075719, NS102414, GM57498),
cell’s recycling process biodiversity today. the Deutsche Forschungsgemeinschaft in Germany
falters, abnormal protein “Shortly after cells invented how to make proteins, (SFB1036, SFB740) and the Max Planck Society in
fragments accumulate, they were also faced with determining how to deal Germany.
potentially causing the with incompletely made proteins,” Joazeiro says. “The
cell’s death. In nerve cells, Claudio Joazeiro analyses suggest that a Rqc2 homolog in the last universal The Scripps Research Institute News on page 17
the process is linked to a
variety of neurodegenerative diseases, including ALS
and dementia.
A new study from the lab of Claudio Joazeiro, Ph.D.,
published online in the journal Cell on May 30, uncovers
how simpler organisms – bacteria and archaea – manage
the recycling of incomplete proteins. The discoveries not
only offer new directions for fighting the virulence of
some of humanity’s most dangerous pathogens, including
listeria, staph and streptococcus, they have implications
for our understanding of how life itself evolved.
Joazeiro’s group found the mechanism isn’t so
different from one they previously uncovered in plant,
animal and fungal cells.
“We know that as cells are making proteins, this
process is occasionally halted due to errors,” says
Joazeiro, who has joint appointments in the Scripps
Research Department of Molecular Medicine in Jupiter,
Fla., and the Center for Molecular Biology of Heidelberg
University in Germany.
“One of the problems with this is that the accumulation
of partially formed proteins may be toxic. So, in our
lab, we’re asking how do cells sense this, and how do
they disassemble these proteins and recycle the building
blocks?”
Organelles called ribosomes serve as the protein-
assembly motors within cells. If they stall during the
process of piecing together the parts – amino acids – cells
have a variety of systems for responding. In human and
other eukaryotic cells, when a ribosome jams, rescue
factors split it open. A protein called Rqc2, also known
as NEMF, zooms in and recruits another protein – the
ubiquitin ligase Ltn1, also called listerin. The Joazeiro
lab previously discovered that Ltn1 marks the truncated
protein fragment on ribosomes with a destruction
tag called ubiquitin. Protease saws then handle the
demolition.
Underscoring the importance of this recycling process,
Joazeiro discovered in 2009 that mutations in Ltn1 can
cause the death of nerve cells in mice, resulting in ALS-
like symptoms. y!
Bacteria have related, but somewhat more direct
systems for addressing halted ribosomes and their protein
fragments, according to the Cell report. Studying the
bacterium B. subtilis, the Joazeiro team found that Rqc2
itself marks the protein fragment with a flag – a polymer Fireworks can be yours everyday
made of the amino acid alanine. Thus flagged, proteases
come to cut up the bad fragment. with the right person! #LoveO Line
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