The effect of protein complexation on the mechanical
stability of Im9
Eleanore R Hann 1, Nadine Kirkpatrick 2, Colin Kleanthous 2, Alastair Smith 3, Sheena E Radford 1 and David J Brockwell 1*
1 University of Leeds
2 University of York
3 Univesity of Leeds
* To whom correspondence should be addressed. E-mail: brock{at}bmb.leeds.ac.uk.
Submitted on December 8, 2006
Revised on January 30, 2007
Accepted on 23 February 2007
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Abstract |
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Force mode microscopy can be used to examine the effect of mechanical manipulation on the non-covalent interactions that stabilise proteins and their complexes. Here we describe the effect of complexation by the high affinity protein ligand E9 on the mechanical resistance of the simple four helical protein, Im9. When concatenated into a construct of alternating I27 domains, Im9 unfolded below the thermal noise limit of the instrument (~20 pN). Complexation of E9 had little effect on the mechanical resistance of Im9 (unfolding force ~30 pN) despite the high avidity of this complex (Kd ~10 fM).
Key Words:
AFM, Im9, mechanical, protein, unfolding
