Double seminar by André Matagne and Frans Mulder

Speakers: Professor André Matagne, Laboratory of Enzymology and Protein Folding, Liege University and Associate Professor Frans AA Mulder, Aarhus University
Host: Professor Birthe Kragelund, SBiN Lab, Section for Biomolecular Sciences

André Matagne
The role of active site flexible loops in catalysis and of zinc in conformational stability of Bacillus cereus 569/H/9 b-lactamase
Metallo-β-lactamases catalyze the hydrolysis of most β-lactam antibiotics and hence represent a major clinical concern. The conformational properties of the BcII β-lactamase have been studied in the presence of chemical denaturants, using a variety of techniques, including enzymatic activity measurement and fluorescence, circular dichroism, and 2D NMR spectroscopies. The data from the various experiments provide evidence that binding of two zinc ions not only increases the conformational stability of the BcII metallo-β-lactamase, but also restores the 3D structural organization that is lost for apoBcII unfolding in the presence denaturant. Moreover the results highlight the importance of a relatively well-defined conformation for two loops that border the active site in order to maintain enzymatic activity.

Frans AA Mulder
New tools for the study of IDPs and the structure determination of MOAG-4, an IDP that modulates in vivo protein aggregation, while remaining disordered upon binding
The analysis of intrinsically disordered proteins (IDPs) is challenging for traditional structure-determination methods due to the eponymous dynamic nature of IDPs. We therefore apply NMR spectroscopy to yield information on the propensity for the formation of local structure [1], identify and quantify electrostatic interactions [2], and determine representative structural ensembles for IDPs [for example, 3]. I’ll briefly discuss recent additions to the NMR toolbox (available at http://www.protein-nmr.org/), and then discuss our work on MOAG-4, an IDP that modulates in vivo protein aggregation in a C elegans model [4]. MOAG-4 forms a saturable complex with alpha-synuclein (AS), based completely on weak electrostatic interactions between two oppositely charged protein domains, without inducing any persistent order [5]. IDP interactions mediated by weak interactions have multiple functional advantages [6], and do not preclude the formation of specific high-affinity complex [7]. Backbone relaxation experiments demonstrate that an initially-exisiting electrostatic interaction between the N- and C-termini of AS is compteted out by MOAG-4 binding.