FIGURE 8.

Structural differences between DnaK and HscA and HscC. (A), Concentrations of the components of the Hsp70 systems in wild type E. coli in non-stress conditions and exponential growth phase. Numbers indicate concentrations in µM according to (Fauvet et al., 2021). <0.1 indicates that these components were below the detection limit of this quantitative mass spectrometry experiment. (B), Weblogo of the C-terminal residues of DnaK, HscA and HscC. DnaK Weblogo, E. coli DnaK was used in a BLAST search against the UniRef90 database of clusters of mutually more than 90% identical sequences, and the C-terminal 18 residues of these representative sequences were used to generate the WebLogo since the C-terminal tail sequences do not align well in multiple sequence alignments due to low complexity (https://weblogo.berkeley.edu/logo.cgi) (Crooks et al., 2004). HscA Weblogo, 194 representative HscA sequences of the UniRef90 database were aligned using CLUSTAL Ω. The 18 residues that correspond to the unstructured tail in DnaK were used to generate the WebLogo. From the crystal structure of HscA-SBD helix E is longer in HscA than in DnaK and only the last 7 residues are unstructured. HscC WebLogo, 191 representative HscC sequences from the UniRef90 database were aligned using CLUSTAL Ω. The 13 residues (9 for E. coli HscC) that correspond to the C-terminal tail of DnaK were used to generate the WebLogo. (C), Homology model of E. coli HscC generated using iTASSER (Yang et al., 2015b; Yang and Zhang, 2015). Lower panel, overlay of the homology model of HscC (dark blue) onto the solution conformation of E. coli DnaK (2KHO, (Bertelsen et al., 2009), shown in light yellow and orange. Orange are the sequence regions that are deleted in HscC.