Session MOB. There are 5 abstracts in this session.

Session: Biomolecular Dynamics 1, time: 10:45-11:10
Microsecond-timescale dynamics of solid proteins
Petra Rovó; Suresh Kumar Vasa; Himanshu Singh; Kristof Grohe; Rasmus Linser
Ludwig-Maximilians-University Munich, Munich, Germany
Fast magic-angle spinning and deuteration have enabled proton-detected approaches for sensitive assessment of protein structure and interactions. I will show that with improvements in assignment strategies at 60 and 111 kHz MAS, increasingly large molecular-weight proteins like complex enzymes can be targeted despite the minimal sample amounts required.
At the same time, amide moieties provide easy access to backbone dynamics via a broad range of different technical approaches. In this talk, I will describe innovations for characterization of microsecond-timescale motion by either 15N or 1H spins as reporters, in particular R1ρ relaxation dispersion close to the rotational resonance condition, as well as their respective implications. We use these methods to decipher motional characteristics of different micro-crystalline proteins and protein complexes.

Session: Biomolecular Dynamics 1, time: 11:10-11:35
Because the light is better here: analysing protein dynamics
Beat Meier1; Albert A Smith1; Nils-Alexander Lakomek1; Thomas Wiegand1; Denis Lacabanne2; Maarten Schledorn1; Anja Böckmann2; Matthias Ernst1
1ETHZ, Zurich, Switzerland; 2IBCP, Lyon, France
Fast magic-angle spinning now provides access to site-specific relaxation data in solid proteins. We shall discuss how such data can best be interpreted. Protein motion is often characterized by a model-free approach using two or three motions with different correlation times. Such a model can lead to a misrepresentation of the real motion, when the real correlation function is more complex than the model which it normally is. We describe how to construct a set of optimized detectors for a given set of relaxation measurements. The analysis using detectors can also be applied to molecular-dynamics data and facilitates a comparison. In addition, the role of dynamics for protein function will be discussed in particular also for motor proteins

Session: Biomolecular Dynamics 1, time: 11:35-12:00
Dynamics of HIV-1 Capsid Protein Assemblies by Integrated MAS NMR, MD, and QM/MM Approach
Mingzhang Wang1; Caitlin Quinn1; Manman Lu1, 2; Juan Perilla1; Huilan Zhang1; Guangjin Hou1; Angela Gronenborn2; Tatyana Polenova1
1University of Delaware, Newark, DE; 2University of Pittsburgh, Pittsburgh, PA
Recent methodological advances will be presented that enable atomic-level characterization of dynamics of large biological HIV-1 assemblies. HIV-1 capsids, assembled from ~1,500 copies of the capsid protein, are an integral part of mature virions. In the assembled state, capsids are remarkably dynamic, with the CA residue motions occurring over a range of timescales from nano- to milliseconds. These motions are functionally important for capsid’s assembly, viral maturation, and interactions with host factors. An integrated MAS NMR, MD, and DFT approach will be presented, to probe the functionally important motions in assemblies of CA and their complexes with host factors. The role of dynamic allosteric regulation in capsid’s assembly, maturation, and escape from the host factor dependence will be discussed.

Session: Biomolecular Dynamics 1, time: 12:00-12:15
Temperature Dependent Allosteric Activation Revealed by NMR
George Lisi; Patrick Loria
Yale University, New Haven, CT

NMR studies of the allosteric enzyme imidazole glycerol phosphate synthase (IGPS) identified a dynamic pathway by which chemical information travels over 25 Å between two binding sites. CPMG relaxation dispersion studies implicate millisecond time scale motions in allosteric signal propagation, where increased conformational flexibility enhances enzymatic activity. The fully activated IGPS complex, containing the allosteric effector PRFAR, is stimulated 5000-fold above basal catalytic levels at room temperature. At elevated temperatures, the allosteric effect of PRFAR is abolished as the unliganded enzyme becomes substantially more flexible, with 50 residues in both apo- and PRFAR-IGPS undergoing millisecond motion at 70 °C, which approximates the native environment of T. maritima IGPS. Kinetic assays demonstrate that PRFAR activates IGPS only 65-fold at 70 °C.


Session: Biomolecular Dynamics 1, time: 12:15-12:30
Transport-Relevant Protein and Water Dynamics on Multiple Timescales in the Influenza M2 Protein
Venkata Shiva Mandala; Martin D. Gelenter; Mei Hong
MIT, Cambridge, MA
The influenza M2 protein forms a tetrameric proton channel that shuttles protons between water and a transmembrane histidine residue. Using SSNMR, we have identified and characterized millisecond-timescale motion of the protein, which is synchronized with proton conduction. 13C chemical shifts of a W41F mutant indicate the presence of two tetramer conformations, whose populations depend on pH. These two conformations interconvert at a rate of ~400 s-1 when the +2 and +3 charge states dominate, providing the first experimental evidence for a transporter-like mechanism where large-scale, cooperative conformational changes correspond to the rate-determining step in proton conduction. The data also give quantitative information about the equilibrium constants and free energies of this conformational change.