Acetylation on E. coli proteins: How it occurs and what proteins with alpha-beta plaits and beta-lactamases have been identified as acetylated
By: Maribel Santos and Riya Pankajkumar Chaudhary
Department: Biochemistry
Faculty Advisor: Dr. Misty L. Kuhn
The purpose of protein acetylation is to add an acetyl group to a lysine residue of a protein to neutralize its charge. Some enzymes that acetylate proteins include Gcn5-related N-acetyltransferases and are generally termed lysine acetyltransferases (KATs). Previous studies have shown hundreds of E. coli proteins are acetylated by KATs. The bigger picture for our research is to understand how a KAT recognizes its substrates. We hypothesized that all of these substrate proteins share a common structural characteristic in order for the KAT protein to be able to recognize them as substrates. To understand this more fully, we grouped the protein substrates based on different structural topologies and selected two topologies to compare: alpha-beta plaits and beta-lactamases. We chose these two for comparison because they are both alpha/beta proteins and have domains with secondary structures that alternate between alpha-helices and beta-strands. Many proteins that have alpha-beta plaits bind nucleotides. The beta-lactamase enzymes are produced by bacteria to evade treatment with antibiotics, by cleaving beta-lactam antibiotics. In our study, we found there were 48 substrate proteins with alpha-beta plaits and 8 proteins with beta-lactamase topologies. Of the proteins with alpha-beta plait domains that were analyzed, nearly half had an acetylated lysine residue on the domain and the other half of the proteins had acetylated lysine residues on other protein domains. Only a few proteins with a beta-lactamase domain had an acetylated lysine residue on this domain. These results show the mechanism for KAT substrate recognition could be more complex than just recognizing a particular structural topology.