Stress Protein Research
Jonathan Hutchinson (e-mail: jph02@ic.ac.uk)
Post-doctoral research assistant - Stress Protein Chemistry
Reto Kohler (e-mail: rjk@ic.ac.uk)
3rd year PhD student - Stress Protein Chemistry
Monika Preuss (e-mail: m.k.preuss@ic.ac.uk)
2nd year PhD student - Stress Protein Chemistry
Our work in the field of stress protein chemistry is concerned with molecular chaperones.
These stress proteins mediate protein-folding in cells and protect proteins against
stress-induced unfolding and aggregation.
Molecular chaperones also have a potential biotechnological application in the refolding of
recombinant proteins which form inclusion bodies. We work on two molecular chaperones,
namely the chaperonin groEL from Escherichia coli and the molecular chaperone HSP47 from
mouse.
Part of our work is concerned with elucidating the molecular recognition which operates
between the groEL chaperonin and a potential protein substrate. From studies of the
chaperonin assisted refolding of denatured mitochondrial malate dehydrogenase, we have
shown that a protein with little or no secondary structure is the preferred substrate for groEL.
To gain insight into the forces of recognition which operate between groEL and a protein
substrate, we have studied the binding of short peptides to the chaperonin. The results indicate
that binding is dominated by the interaction of hydrophobic amino acid side chains with groEL,
supplemented by short range electrostatic interactions between groEL and the side-chains of
positively charged amino acids. Positively charged side-chains also promote recognition of
protein substrates by groEL whilst the side-chains of negatively charged amino acids
discourage recognition. The importance of secondary structure for molecular recognition and
the binding of protein substrates by groEL is now under close investigation.
Another aspect of our work with groEL involves the use of this chaperonin, with the
co-chaperonin groES, to refold proteins efficiently on a preparative scale in a special
"bioreactor". This system includes novel ways to recycle the chaperonin components and
separate the refolded substrate protein from the refolding mixture. The system is also being
applied to the folding of recombinant proteins which form inclusion bodies upon
over-expression in bacterial hosts, a procedure which could be of significant interest to the
biotechnology industry.
Finally, HSP 47 is believed to play a crucial role in the biogenesis of collagen through binding
to nascent procollagen and assisting the formation of procollagen triple-helix in an as yet not
completely understood way. We are working in close collaboration with Prof Kazuhiro Nagata's
group, at Kyoto University, to understand the cellular role and molecular mechanism of this
protein in more detail. Recently, we constructed a useful molecular model of HSP47 and
showed that the pH-dependent collagen binding mechanism of HSP47 is probably caused by
reversible pH-induced secondary and tertiary structural transitions in HSP47 itself. We are
currently further investigating the pH-induced structural transitions of HSP47 as well as
procollagen substrate recognition. Shortly, we hope to obtain the X-ray crystal structure of
HSP47.
