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Title: Biophysical studies on two beta-sandwich proteins
Author: Fong, S.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1998
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An immunoglobulin superfamily domain, Ig 18' from the nematode Caenorhabditis elegans, was over-expressed and purified from E. Coli. The solution properties of the folded and denatured states of Ig 18' were characterised by multi-dimensional NMR. The NMR structure of the folded Ig 18' has been determined based on 1207 distance and 48 dihedral restraints using a hybrid distance geometry-stimulated annealing protocol. The atomic rms distributions about the mean coordinate for the ensemble of structures are 0.55(±0.09) Å for backbone atoms and 1.10(±0.08) Å for all heavy atoms. The domain has a topology very similar to telokin and belongs to the I set of the immunoglobulin superfamily. The close agreement between the predicted and observed structures of Ig 18' demonstrates that the I set sequence profile can be applied for the identification and structure prediction of immunoglobulin-like domains. Model-free analysis of the relaxation parameters of the folded Ig 18' suggests that several regions possess dynamic behaviours that are different from the rest of the domain. The N- terminal stretch of the C-D loop is involved in fast internal motion with relatively less spatial restriction. In contrast, slow exchange contributions are likely to be involved in the A-A', A'-B, and E-F loops. The structural and dynamic properties of Ig 18' have been characterised at 285 K, in the presence of 4.2 M and 6.0 M urea. Analysis of chemical shift deviations, 3JHNHα coupling constants, sequential NOE patterns, and 15N relaxation data reveals that although the two urea-denatured states are highly disordered, some local turn-like residual structure does exist. Moreover, some distinct differences between the properties of the two denatured states are observed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available