%0 Journal Article
%T Protein Acetylation in Archaea, Bacteria, and Eukaryotes
%A J£¿rg Soppa
%J Archaea
%D 2010
%I Hindawi Publishing Corporation
%R 10.1155/2010/820681
%X Proteins can be acetylated at the alpha-amino group of the N-terminal amino acid (methionine or the penultimate amino acid after methionine removal) or at the epsilon-amino group of internal lysines. In eukaryotes the majority of proteins are N-terminally acetylated, while this is extremely rare in bacteria. A variety of studies about N-terminal acetylation in archaea have been reported recently, and it was revealed that a considerable fraction of proteins is N-terminally acetylated in haloarchaea and Sulfolobus, while this does not seem to apply for methanogenic archaea. Many eukaryotic proteins are modified by differential internal acetylation, which is important for a variety of processes. Until very recently, only two bacterial proteins were known to be acetylation targets, but now 125 acetylation sites are known for E. coli. Knowledge about internal acetylation in archaea is extremely limited; only two target proteins are known, only one of which¡ªAlba¡ªwas used to study differential acetylation. However, indications accumulate that the degree of internal acetylation of archaeal proteins might be underestimated, and differential acetylation has been shown to be essential for the viability of haloarchaea. Focused proteomic approaches are needed to get an overview of the extent of internal protein acetylation in archaea. 1. Introduction Many different forms of posttranslational modifications of proteins have been characterized. Posttranslational modifications can influence many different features of proteins, for example, their folding, activity, stability, antigenicity, intracellular localization, and interaction with other proteins or with nucleic acids. The fraction of posttranslationally modified proteins and thus the importance of posttranslational modification is generally believed to be very different for eukaryotes¡ªhaving a high fraction of modified proteins¡ªand prokaryotes, which are thought to harbor only very few modified proteins. For eukaryotes it is thought that acetylation is the most common covalent modification out of 200 types that have been reported [1]. It has also been argued that acetylation is a regulatory modification of the same importance as phosphorylation [2]. The arguments were that acetylation, like phosphorylation, affects many different proteins, can have a variety of consequences, and can regulate key cellular processes in response to extracellular signals [2]. Nevertheless, the wealth of experimental data on protein phosphorylation in eukaryotes is much higher than on acetylation, and in addition, it was typically
%U http://www.hindawi.com/journals/archaea/2010/820681/