Thermodynamics of folding and binding in an affibody:affibody complex
2006 (English)In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 359, no 5, 1305-1315 p.Article in journal (Refereed) Published
Affibody binding proteins are selected from phage-displayed libraries of variants of the 58 residue Z domain. Z(Taq) is an affibody originally selected as a binder to Taq DNA polymerase. The anti-Z(Taq) affibody was selected as a binder to Z(Taq) and the Z(Taq):anti-Z(Taq) complex is formed with a dissociation constant K-d = 0.1 mu M. We have determined the structure of the Z(Taq):anti-Z(Taq) complex as well as the free state structures of Z(Taq) and anti-Z(Taq) using NMR. Here we complement the structural data with thermodynamic studies of Z(Taq) and anti-Z(Taq) folding and complex formation. Both affibody proteins show cooperative two-state thermal denaturation at melting temperatures T-M similar to 56 degrees C. Z(Taq):anti-Z(Taq) complex formation at 25 degrees C in 50 mM NaCl and 20 mM phosphate buffer (pH 6.4) is enthalpy driven with Delta H degrees(bind) = -9.0(+/- 0.1) kcal mol(-1). The heat capacity change Delta C-P degrees,(bind) = -0.43(+/- 0.01) kcal mol(-1) K-1 is in accordance with the predominantly non-polar character of the binding surface, as judged from calculations based on changes in accessible surface areas. A further dissection of the small binding entropy at 25 degrees C (-T Delta S degrees(bind) = -0.6(+/- 0.1) kcal mol(-1)) suggests that a favourable desolvation of non-polar surface is almost completely balanced by unfavourable conformational entropy changes and loss of rotational and translational entropy. Such effects can therefore be limiting for strong binding also when interacting protein components are stable and homogeneously folded. The combined structure and thermodynamics data suggest that protein properties are not likely to be a serious limitation for the development of engineered binding proteins based on the Z domain.
Place, publisher, year, edition, pages
2006. Vol. 359, no 5, 1305-1315 p.
protein engineering, protein stability, molecular recognition, binding thermodynamics, calorimetry
Other Industrial Biotechnology
IdentifiersURN: urn:nbn:se:kth:diva-6409DOI: 10.1016/j.jmb.2006.04.041ISI: 000238988400012ScopusID: 2-s2.0-33746927966OAI: oai:DiVA.org:kth-6409DiVA: diva2:11110
QC 201101182006-11-222006-11-222012-03-20Bibliographically approved