Dr Sigurd Wilbanks

Senior Lecturer

Biochemistry Department
School of Medical Sciences
University of Otago
P.O. Box 56
710 Cumberland St
Dunedin 9054 , New Zealand
Tel.: +64 3 479-7850
FAX: +64 3 479-7866
e-mail:sigurd.wilbanks@otago.ac.nz

Molecular Chaperones:

How do molecular chaperones distinguish proteins which are damaged or threatened by inappropriate interactions from those proteins which are mature, healthy and in no need of assistance? We study the structure of chaperones and their substrates to determine how the chaperone can recognize and control the secondary and tertiary fold of its substrates. Members of the lab are skilled in molecular cloning, protein purification, enzymology and X-ray crystallography.

How does the structure of trigger factor contribute to its activity?

How does Hsp70 activate the tumor suppressor WT1?

Can we exploit the activity of the PRP8 intein of Cryptococcus neoformans?

How do sea urchins control the growth of their spines?

How does the structure of trigger factor contribute to its activity? The bacterial "trigger factor" chaperone assists protein folding in two ways. First, it binds ribosomes, protecting newly synthesised polypeptide chains, preventing misfolding and enabling secretion. Second, it isomerises the peptide bond adjacent to proline residues, shifting that bond between the trans and cis conformations. This activity, together with sequence data, places trigger factor within the FKBP family of prolyl isomerases and provides clues to its structure and mechanism. Taking a comparative approach, we have cloned and expressed trigger factor from E. coli (in collaboration with Professor Bernd Bukau of Heidelburg), Haemophilus influenzae, Mycobacterium tuberculosis, Aquifex aeolicus and Thermatoga maritima. Comparison of the different activities, sequences and three-dimensional structures of these proteins gives us clues to which structures underlie which functions.

How does Hsp70 activate the tumor suppressor WT1? The tumor suppressor WT1 requires the chaperone Hsp70 for activity in vivo. We are testing the hypothesis that Hsp70 alters the structure of WT1. In collaboration with Dr Michael Eccles of the Pathology Department we have established an in vitro system to study their interaction. WT1 is a transcription factor active in uro-genital development. Mutations of WT1 have been implicated in developmental abnormalities and in Wilms' tumor, a childhood cancer. Hsp70 is an abundant, ubiquitous chaperone of mammals.

Can we exploit the activity of the PRP8 intein of Cryptococcus neoformans? Inteins are self-splicing protein domains, encoded by mobile genetic elements. In collaboration with Drs Russell Poulter and Margi Butler of the Biochemistry Department we are investigating the function of the PRP8 intein, found in a pathogenic fungus responsible for ~8% of AIDS deaths. Autocatalytic self-excision of the intein is crucial to maturation of the essential splicesomal protein PRP8. Crucial to pathogen survival and absent from all human proteins, the intein a promising drug target. In addition, we are interested in how the intein's ability to ligate together the flanking protein domains can be exploited to form novel proteins in vitro and in vivo.

How do sea urchins control the growth of their spines? In collaboration with Dr Kate McGrath of the Chemistry Department we have extracted from New Zealand sea urchin spines glyco-proteins which control the growth of the calcite crystals which make up the sea urchin's exo-skeleton. These proteins and their constituent sugars help adjust the balance between thermodynamic and kinetic constraints on calcite growth, thus controlling crystal morphology.

Support for our work on trigger factor has come from the Otago Research Committee, the Dean's Bequest Fund and the Lottery Grants Board. Esther's work on inteins was supported by the Lottery Grants Board. Callum's sea urchin work was supported by a Marsden grant to Dr Kathryn McGrath. Rob's WT1 work is supported by the Child Health Research Foundation.