Novel “Order-Disorder-Order” Mechanism in Adenylate Kinase Conformational Change

Abstract

Conformational changes are intimately coupled to the biological activity of many proteins. It is challenging to unravel the molecular mechanism of conformational change since intermediate states are short-lived and usually not observable by spectroscopic methods. Adenylate kinase (Adk) is an enzyme that undergoes a large conformational rearrangement in response to ATP binding, and serves as an excellent model to study the interplay between structure, dynamics and activity. We have studied the molecular mechanism of Adk conformational change (associated with ATP binding) with a combined protein engineering and spectroscopic approach. We identified a novel mechanism that includes local unfolding/refolding of a segment in the ATP binding subdomain in an otherwise folded enzyme. Thus, the mechanism for conformational change can be denoted as an “order-disorder-order” transition, where “order-disorder” transitions have been observed for other proteins previously. Our results show that the functional and folding energy landscapes of adk in fact are overlapping. This observation suggests that functional properties may be added to proteins by use of cooperative folding/unfolding transitions. in addition, we present data that conspire to define the structure of an initial and transient Adk-ATP complex. This accomplishment provides detailed knowledge of a structural state that is both difficult to capture and important for understanding of the catalytic power of Adk. Taken together we can portrait a detailed picture of the structural states that form the basis for Adk catalysis.Reference:Ulrika Olsson & Magnus Wolf-Watz. Nature Communications. 2010.