Multi-functionality of aminoacyl-tRNA synthetases

The role of aminoacyl-tRNA synthetases (aaRSs) in translation is known by everyone in the field of molecular biology. What people often do not realize, however, is that aaRSs are involved in a lot of processes apart from translation. AaRSs are involved in processes like transcriptional and translational regulation, antibiotic resistance, synthesis of unnatural amino acids, cell signaling and many more. This multi-functionality of aaRSs occurs in all three domains of life. Here I will discuss the extend of this multifunctionality in bacteria. I will compare the complexity of bacterial aaRS multi-functionality to that of eukaryotes. Finally I will describe new insights in bacterial complexity obtained from interactome studies. This literature study shows that bacterial aaRS multi-functionality is a lot less complex than that of eukaryotes. The most important point, however, is that the complexity of the functions of bacterial aaRSs may be drastically underestimated.

Steric exclusion and protein conformation determine the localization of plasma membrane transporters

Contains fulltext : 200405.pdf (publisher's version ) (Open Access)The plasma membrane (PM) of Saccharomyces cerevisiae contains membrane compartments, MCC/eisosomes and MCPs, named after the protein residents Can1 and Pma1, respectively. Using high-resolution fluorescence microscopy techniques we show that Can1 and the homologous transporter Lyp1 are able to diffuse into the MCC/eisosomes, where a limited number of proteins are conditionally trapped at the (outer) edge of the compartment. Upon addition of substrate, the immobilized proteins diffuse away from the MCC/eisosomes, presumably after taking a different conformation in the substrate-bound state. Our data indicate that the mobile fraction of all integral plasma membrane proteins tested shows extremely slow Brownian diffusion through most of the PM. We also show that proteins with large cytoplasmic domains, such as Pma1 and synthetic chimera of Can1 and Lyp1, are excluded from the MCC/eisosomes. We hypothesize that the distinct localization patterns found for these integral membrane proteins in S. cerevisiae arises from a combination of slow lateral diffusion, steric exclusion, and conditional trapping in membrane compartments