Poster Annual Conference of the Genetics Society of Australasia with the NZ Society for Biochemistry & Molecular Biology

A FRET reporter of conformation in Hsc70 (779)

Malcolm T Rutledge 1 , Sigurd M Wilbanks 1
  1. Department of Biochemistry, University of Otago, Dunedin, New Zealand

Hsp70s are the most well conserved protein family known, and yet little of their mechanism within the cell is understood. Hsc70 is a constitutively expressed member of the Hsp70 family found in the cytosol of all eukaryotic cells. Hsc70 has many functions within the cell, including assisting with the folding of nascent peptides, targeting proteins for degradation, and remodelling protein complexes. Hsp70s consist of two highly conserved domains, the nucleotide binding domain (NBD) and the substrate binding domain (SBD), joined by a flexible linker region. The juxtaposition of the two domains is dependent on the nucleotide bound by the NBD. Many previous studies of Hsp70s have relied on the bacterial form, DnaK. In this study, Hsc70 constructs were produced based on previous DnaK versions. Using these constructs, the nucleotide dependant conformational shifts of Hsp70s were probed by Förster resonance energy transfer (FRET) using fluorescent dyes attached to each domain of the protein. This allowed direct comparisons to be made between Hsc70 and DnaK. One of the aims of this study was to find an Hsc70 construct that would produce a strong FRET signal, which could them be used in future single molecule and in vivo studies. The variant E318C/T427C/C574S/C603S gave the strongest signal of the four variants tested. It also showed that while broadly similar, Hsc70 and DnaK conformations are not the same, with ADP-bound DnaK spending less time with the linker region exposed to solvent than does the ADP-bound Hsc70 does.