Genetic incorporation of Nε-acetyllysine reveals a novel acetylation-sumoylation switch in yeast

Orthogonal Translation for Site-Specific Installation of Post-translational Modifications

Post-translational modifications (PTMs) endow proteins with new properties to respond to environmental changes or growth needs. With the development of advanced proteomics techniques, hundreds of distinct types of PTMs have been observed in a wide range of proteins from bacteria, archaea, and eukarya. To identify the roles of these PTMs, scientists have applied various approaches. However, high dynamics, low stoichiometry, and crosstalk between PTMs make it almost impossible to obtain homogeneously modified proteins for characterization of the site-specific effect of individual PTM on target proteins. To solve this problem, the genetic code expansion (GCE) strategy has been introduced into the field of PTM studies. Instead of modifying proteins after translation, GCE incorporates modified amino acids into proteins during translation, thus generating site-specifically modified proteins at target positions. In this review, we summarize the development of GCE systems for orthogonal translation for site-specific installation of PTMs.

Functional analysis of protein post-translational modifications using genetic codon expansion

Post-translational modifications (PTMs) of proteins not only exponentially increase the diversity of proteoforms, but also contribute to dynamically modulating the localization, stability, activity, and interaction of proteins. Understanding the biological consequences and functions of specific PTMs has been challenging for many reasons, including the dynamic nature of many PTMs and the technical limitations to access homogenously modified proteins. The genetic code expansion technology has emerged to provide unique approaches for studying PTMs. Through site-specific incorporation of unnatural amino acids (UAAs) bearing PTMs or their mimics into proteins, genetic code expansion allows the generation of homogenous proteins with site-specific modifications and atomic resolution both in vitro and in vivo. With this technology, various PTMs and mimics have been precisely introduced into proteins. In this review, we summarize the UAAs and approaches that have been recently developed to site-specifically install PTMs and their mimics into proteins for functional studies of PTMs.

Noncanonical Amino Acids in Synthetic Biosafety and Post-translational Modification Studies

The incorporation of noncanonical amino acids (ncAAs) has been extensively studied because of its broad applicability. In the past decades, various in vitro and in vivo ncAA incorporation approaches have been developed to generate synthetic recombinant proteins. Herein, we discuss the methodologies for ncAA incorporation, and their use in diverse research areas, such as in synthetic biosafety and for studies of post-translational modifications.

Recent Development of Genetic Code Expansion for Posttranslational Modification Studies

Nowadays advanced mass spectrometry techniques make the identification of protein posttranslational modifications (PTMs) much easier than ever before. A series of proteomic studies have demonstrated that large numbers of proteins in cells are modified by phosphorylation, acetylation and many other types of PTMs. However, only limited studies have been performed to validate or characterize those identified modification targets, mostly because PTMs are very dynamic, undergoing large changes in different growth stages or conditions. To overcome this issue, the genetic code expansion strategy has been introduced into PTM studies to genetically incorporate modified amino acids directly into desired positions of target proteins. Without using modifying enzymes, the genetic code expansion strategy could generate homogeneously modified proteins, thus providing powerful tools for PTM studies. In this review, we summarized recent development of genetic code expansion in PTM studies for research groups in this field.

The Unsolved Problem of How Cells Sense Micron-Scale Curvature

Membrane curvature is a fundamental feature of cells and their organelles. Much of what we know about how cells sense curved surfaces comes from studies examining nanometer-sized molecules on nanometer-scale curvatures. We are only just beginning to understand how cells recognize curved topologies at the micron scale. In this review, we provide the reader with an overview of our current understanding of how cells sense and respond to micron-scale membrane curvature.

Chemical biology approaches for studying posttranslational modifications

Posttranslational modification (PTM) is a key mechanism for regulating diverse protein functions, and thus critically affects many essential biological processes. Critical for systematic study of the effects of PTMs is the ability to obtain recombinant proteins with defined and homogenous modifications. To this end, various synthetic and chemical biology approaches, including genetic code expansion and protein chemical modification methods, have been developed. These methods have proven effective for generating site-specific authentic modifications or structural mimics, and have demonstrated their value for in vitro and in vivo functional studies of diverse PTMs. This review will discuss recent advances in chemical biology strategies and their application to various PTM studies.