The bacterial protein Lem3 is positioned outside the vacuole and reverses the modification of the host protein to ensure that the protein "bricks" are free to be used in creation of the bacterial structure.
This study was the first to identify proteins that directly add and remove the phosphorylcholine moiety, Luo said.
"We were surprised to find that the bacterial proteins use the phosphorylcholination process and to discover that this process is reversible," he said. "This is evidence of a new way signals are relayed within cells, and we are eager to investigate it."
The team also found that the phosphorylcholination reaction is carried out at a specific site on the protein called the Fic domain. Previous studies had shown this site induced a different reaction called AMPylation.
It is rare for a domain to catalyze more than one reaction, and it was thought this site's only responsibility was to transfer the chemical group necessary for AMPylation, Luo said.
"Revealing that this domain has dual roles is very important to identify or screen for compounds to inhibit its activity and fight disease," he said. "This domain has a much broader involvement in biochemical reactions than we thought and may be a promising target for effective treatments."
During infection bacteria deliver hundreds of proteins into healthy cells that alter cellular processes to turn the hostile environment into one hospitable to bacterial replication, but the specific roles of only about 20 proteins are known, Luo said.
"In order to pinpoint proteins that would be good targets for new antibiotics, we need to determine their
|Contact: Elizabeth K. Gardner|