Duvelisib Refraining From A Sense of obscurity

, 2011) is consistent with the finding that proteins of COG class L (DNA replication, recombination and repair), such as the nucleotide excision repair protein UvrA, are overrepresented among the DnaK-enriched substrates ( Figure?S2). UvrA is a large, heterooligomeric protein with two c.37 domains; which aggregates to 30% of total in the absence of DnaK/DnaJ already at 30��C. The sensitivity of ��dnaK cells to antibiotics inhibiting protein synthesis ( Nichols et?al., 2011) would correlate with the extensive interaction of DnaK with ribosomal proteins and the degradation in ��KJ cells of several DnaK interactors of COG class E (amino acid transport and metabolism). Finally, the sensitivity of ��dnaK cells to acidic conditions ( Nichols et?al., 2011) is consistent with the 80%?97% degradation in ��KJ cells of the periplasmic chaperones of acid-denatured proteins, hdeA, and hdeB. Our analysis of the DnaK interactome in Selleck Duvelisib cells lacking TF or depleted of GroEL/ES underscores the significance of DnaK as a central hub in the chaperone network. The observed accumulation of a subset of proteins on DnaK in the absence of TF defines in a quantitative manner the functional redundancy between these two chaperone systems described earlier (Deuerling et?al., 1999?and?Teter et?al., 1999). Interestingly, these substrates comprise mostly ribosomal and other small Selleck PFI-2 (flupentixol been suggested (Martinez-Hackert and Hendrickson, 2009). In contrast, the DnaK system is unable to replace the role of TF in the biogenesis of a set of secretory proteins, prominently including ��-barrel proteins of the outer membrane (Figure?7B). These proteins undergo partial degradation in cells lacking TF, suggesting a specific role of TF in translocation of outer membrane preproteins across the inner membrane. Such a function of TF would be consistent with the initial identification of TF as a chaperone of proOmpA translocation in?vitro (Crooke et?al., 1988) and with the finding that TF modulates the kinetics of protein export (Lee and Bernstein, 2002?and?Ullers et?al., 2007). It is also of interest in this context that TF structurally resembles the periplasmic chaperone for outer membrane proteins, SurA (Bitto and McKay, 2002?and?Ferbitz et?al., 2004). An effective functional cooperation apparently exists between TF and the DnaK system in the folding of a group of large multidomain proteins that aggregate substantially only in the absence of both chaperones.