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Catalysis and substrate selection by histone/protein lysine acetyltransferases.

ABSTRACT: Reversible protein acetylation is controlled by the opposing actions of protein lysine acetyltransferases and deacetylations. Recent developments on the structure and biochemical mechanisms of histone acetyltransferases (HATs) have provided new insight into catalysis and substrate selection. Diverse families of HATs appear to perform a conserved mechanism of acetyl transfer, where the lysine-containing substrate directly attacks enzyme-bound acetyl-CoA. The ability of HATs to form distinct multi-subunit complexes provides a means to regulate HAT activity by altering substrate specificity, targeting to specific loci, enhancing acetyltransferase activity, restricting access of non-target proteins, and coordinating the multiple enzyme activities of the complex. In the case of newly discovered Rtt109 HAT, association with distinct histone chaperones directs substrate selection between N-terminal lysines (H3K9, H3K23) and those (H3K56) within the histone fold domain. Moreover, the ability of some HATs to utilize longer chain acyl-CoA (i.e. propionyl-CoA) as alternative substrates suggests a potential direct link between the metabolic state of the cell and transcriptional regulation.

SUBMITTER: Berndsen CE

PROVIDER: S-EPMC2723715 | biostudies-literature | 2008 Dec

REPOSITORIES: biostudies-literature

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Catalysis and substrate selection by histone/protein lysine acetyltransferases.

Berndsen Christopher E CE Denu John M JM

Current opinion in structural biology 20081201 6

Reversible protein acetylation is controlled by the opposing actions of protein lysine acetyltransferases and deacetylations. Recent developments on the structure and biochemical mechanisms of histone acetyltransferases (HATs) have provided new insight into catalysis and substrate selection. Diverse families of HATs appear to perform a conserved mechanism of acetyl transfer, where the lysine-containing substrate directly attacks enzyme-bound acetyl-CoA. The ability of HATs to form distinct multi ...[more]

PMID: 19056256

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Project description:Histone acetyltransferases (HATs) are epigenetic enzymes that install acetyl groups onto lysine residues of cellular proteins such as histones, transcription factors, nuclear receptors, and enzymes. HATs have been shown to play a role in diseases ranging from cancer and inflammatory diseases to neurological disorders, both through acetylations of histone proteins and non-histone proteins. Several HAT inhibitors, like bi-substrate inhibitors, natural product derivatives, small molecules, and protein-protein interaction inhibitors, have been developed. Despite their potential, a large gap remains between the biological activity of inhibitors in in vitro studies and their potential use as therapeutic agents. To bridge this gap, new potent HAT inhibitors with improved properties need to be developed. However, several challenges have been encountered in the investigation of HATs and HAT inhibitors that hinder the development of new HAT inhibitors. HATs have been shown to function in complexes consisting of many proteins. These complexes play a role in the activity and target specificity of HATs, which limits the translation of in vitro to in vivo experiments. The current HAT inhibitors suffer from undesired properties like anti-oxidant activity, reactivity, instability, low potency, or lack of selectivity between HAT subtypes and other enzymes. A characteristic feature of HATs is that they are bi-substrate enzymes that catalyze reactions between two substrates: the cofactor acetyl coenzyme A (Ac-CoA) and a lysine-containing substrate. This has important-but frequently overlooked-consequences for the determination of the inhibitory potency of small molecule HAT inhibitors and the reproducibility of enzyme inhibition experiments. We envision that a careful characterization of molecular aspects of HATs and HAT inhibitors, such as the HAT catalytic mechanism and the enzyme kinetics of small molecule HAT inhibitors, will greatly improve the development of potent and selective HAT inhibitors and provide validated starting points for further development towards therapeutic agents.

Project description:Posttranslational modifications, such as Nε-lysine acetylation, regulate protein function. Nε-lysine acetylation can occur either nonenzymatically or enzymatically. The nonenzymatic mechanism uses acetyl phosphate (AcP) or acetyl coenzyme A (AcCoA) as acetyl donor to modify an Nε-lysine residue of a protein. The enzymatic mechanism uses Nε-lysine acetyltransferases (KATs) to specifically transfer an acetyl group from AcCoA to Nε-lysine residues on proteins. To date, only one KAT (YfiQ, also known as Pka and PatZ) has been identified in Escherichia coli Here, we demonstrate the existence of 4 additional E. coli KATs: RimI, YiaC, YjaB, and PhnO. In a genetic background devoid of all known acetylation mechanisms (most notably AcP and YfiQ) and one deacetylase (CobB), overexpression of these putative KATs elicited unique patterns of protein acetylation. We mutated key active site residues and found that most of them eliminated enzymatic acetylation activity. We used mass spectrometry to identify and quantify the specificity of YfiQ and the four novel KATs. Surprisingly, our analysis revealed a high degree of substrate specificity. The overlap between KAT-dependent and AcP-dependent acetylation was extremely limited, supporting the hypothesis that these two acetylation mechanisms play distinct roles in the posttranslational modification of bacterial proteins. We further showed that these novel KATs are conserved across broad swaths of bacterial phylogeny. Finally, we determined that one of the novel KATs (YiaC) and the known KAT (YfiQ) can negatively regulate bacterial migration. Together, these results emphasize distinct and specific nonenzymatic and enzymatic protein acetylation mechanisms present in bacteria.IMPORTANCENε-Lysine acetylation is one of the most abundant and important posttranslational modifications across all domains of life. One of the best-studied effects of acetylation occurs in eukaryotes, where acetylation of histone tails activates gene transcription. Although bacteria do not have true histones, Nε-lysine acetylation is prevalent; however, the role of these modifications is mostly unknown. We constructed an E. coli strain that lacked both known acetylation mechanisms to identify four new Nε-lysine acetyltransferases (RimI, YiaC, YjaB, and PhnO). We used mass spectrometry to determine the substrate specificity of these acetyltransferases. Structural analysis of selected substrate proteins revealed site-specific preferences for enzymatic acetylation that had little overlap with the preferences of the previously reported acetyl-phosphate nonenzymatic acetylation mechanism. Finally, YiaC and YfiQ appear to regulate flagellum-based motility, a phenotype critical for pathogenesis of many organisms. These acetyltransferases are highly conserved and reveal deeper and more complex roles for bacterial posttranslational modification.

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Catalysis and substrate selection by histone/protein lysine acetyltransferases.

Publications

Catalysis and substrate selection by histone/protein lysine acetyltransferases.

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