István Nagy - Academia.edu (original) (raw)

Papers by István Nagy

Trends in Microbiology, 1999

I ntracellular proteases in prokaryotic cells perform many tasks, including cleavage of signal pe... more I ntracellular proteases in prokaryotic cells perform many tasks, including cleavage of signal peptides during protein export, timely inactivation of regulatory proteins, and removal of aberrant nonfunctional proteins 1. Obviously, proteolysis inside prokaryotic cells needs to be controlled to avoid unwanted degradation. Spatial safeguarding can be provided by directing a protease to a specific compartment of the cell, such as the periplasmic space of Gram-negative bacteria. Autocompartmentalization, as a common strategy to curtail the potential hazard associated with intracellular protein breakdown, has recently emerged from the elucidation of the structure of a subset of cytoplasmic proteases in prokaryotes 2. Isolation of proteolytic activity is achieved by self-assembly of proteolytic subunits into a cylinder-shaped complex, in which the active sites are confined to nanocompart-ments in their interior (Fig. 1). Narrow entrances to the cylinder restrict access to unfolded proteins. The ATPase complexes that can bind to both ends of such barrels are thought to be involved in the initial binding, unfolding and translocation of substrates. Proteases creating nanocompartments The proteasome, which has become the paradigm of a selfcompartmentalizing protease 3 , was first discovered in eukaryotic cells, where it constitutes the major non-lysosomal proteolytic system 4. The proteolytic core (20S proteasome), capped with 19S regulatory complexes (including several ATPases), is designated the 26S proteasome and mediates the ATP-dependent degradation of ubiquitin-bound proteins 5. The archaeal counterpart of the 20S proteasome was identified in Thermoplasma acidophilum about a decade ago 6. The discovery of The proteasome represents the major nonlysosomal proteolytic system in eukaryotes. It confines proteolytic activity to an inner compartment that is accessible to unfolded proteins only. The strategy of controlling intracellular breakdown of proteins by self-compartmentalization is also used by different types of prokaryotic energy-dependent proteases. Genomic sequencing data reveal that various combinations of these energy-dependent proteases occur in prokaryotic cells from different lineages.

Trends in Microbiology, 1999

I ntracellular proteases in prokaryotic cells perform many tasks, including cleavage of signal pe... more I ntracellular proteases in prokaryotic cells perform many tasks, including cleavage of signal peptides during protein export, timely inactivation of regulatory proteins, and removal of aberrant nonfunctional proteins 1. Obviously, proteolysis inside prokaryotic cells needs to be controlled to avoid unwanted degradation. Spatial safeguarding can be provided by directing a protease to a specific compartment of the cell, such as the periplasmic space of Gram-negative bacteria. Autocompartmentalization, as a common strategy to curtail the potential hazard associated with intracellular protein breakdown, has recently emerged from the elucidation of the structure of a subset of cytoplasmic proteases in prokaryotes 2. Isolation of proteolytic activity is achieved by self-assembly of proteolytic subunits into a cylinder-shaped complex, in which the active sites are confined to nanocompart-ments in their interior (Fig. 1). Narrow entrances to the cylinder restrict access to unfolded proteins. The ATPase complexes that can bind to both ends of such barrels are thought to be involved in the initial binding, unfolding and translocation of substrates. Proteases creating nanocompartments The proteasome, which has become the paradigm of a selfcompartmentalizing protease 3 , was first discovered in eukaryotic cells, where it constitutes the major non-lysosomal proteolytic system 4. The proteolytic core (20S proteasome), capped with 19S regulatory complexes (including several ATPases), is designated the 26S proteasome and mediates the ATP-dependent degradation of ubiquitin-bound proteins 5. The archaeal counterpart of the 20S proteasome was identified in Thermoplasma acidophilum about a decade ago 6. The discovery of The proteasome represents the major nonlysosomal proteolytic system in eukaryotes. It confines proteolytic activity to an inner compartment that is accessible to unfolded proteins only. The strategy of controlling intracellular breakdown of proteins by self-compartmentalization is also used by different types of prokaryotic energy-dependent proteases. Genomic sequencing data reveal that various combinations of these energy-dependent proteases occur in prokaryotic cells from different lineages.