Engineering topics

Stadler, Andreas M.

Publications and source records attributed to Stadler, Andreas M..

4 records

DOE OSTI2024

Functional in vitro diversity of an intrinsically disordered plant protein during freeze–thawing is encoded by its structural plasticity

Intrinsically disordered late embryogenesis abundant (LEA) proteins play a central role in the tolerance of plants and other organisms to dehydration brought upon, for example, by freezing temperatures, high salt concentration, drought or desiccation, and many LEA proteins have been found to stabilize dehydration-sensitive cellular structures. Their conformational ensembles are highly sensitive to the environment, allowing them to undergo conformational changes and adopt ordered secondary and quaternary structures and to participate in formation of membraneless organelles. In an interdisciplinary approach, we discovered how the functional diversity of the Arabidopsis thaliana LEA protein COR15A found in vitro is encoded in its structural repertoire, with the stabilization of membranes being achieved at the level of secondary structure and the stabilization of enzymes accomplished by the formation of oligomeric complexes. We provide molecular details on intra- and inter-monomeric helix–helix interactions, demonstrate how oligomerization is driven by an α-helical molecular recognition feature (α-MoRF) and provide a rationale that the formation of noncanonical, loosely packed, right-handed coiled-coils might be a recurring theme for homo- and hetero-oligomerization of LEA proteins.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2020

Membrane stiffness and myelin basic protein binding strength as molecular origin of multiple sclerosis

Myelin basic protein (MBP) and its interaction with lipids of the myelin sheath plays an important part in the pathology of multiple sclerosis (MS). Previous studies observed that changes in the myelin lipid composition lead to instabilities and enhanced local curvature of MBP-lipid multilayer structures. We investigated the molecular origin of the instability and found that the diseased lipid membrane has a 25% lower bending rigidity, thus destabilizing smooth >1µm curvature radius structures such as in giant unilamellar vesicles. MBP-mediated assembling of lipid bilayers proceeds in two steps, with a slow second step occurring over many days where native lipid membranes assemble into well-defined multilayer structures, whereas diseased lipid membranes form folded assemblies with high local curvature. For both native and diseased lipid mixtures we find that MBP forms dense liquid phases on top of the lipid membranes mediating attractive membrane interactions. Furthermore, we observe MBP to insert into its bilayer leaflet side in case of the diseased lipid mixture, whereas there is no insertion for the native mixture. Insertion increases the local membrane curvature, and could be caused by a decrease of the sphingomyelin content of the diseased lipid mixture. These findings can help to open a pathway to remyelination strategies.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2020

Transition between protein-like and polymer-like dynamic behavior: Internal friction in unfolded apomyoglobin depends on denaturing conditions

Equilibrium dynamics of different folding intermediates and denatured states is strongly connected to the exploration of the conformational space on the nanosecond time scale and might have implications in understanding protein folding. For the first time, the same protein system apomyoglobin has been investigated using neutron spin-echo spectroscopy in different states: native-like, partially folded (molten globule) and completely unfolded, following two different unfolding paths: using acid or guanidinium chloride (GdmCl). While the internal dynamics of the native-like state can be understood using normal mode analysis based on high resolution structural information of myoglobin, for the unfolded and even for the molten globule states, models from polymer science are employed. The Zimm model accurately describes the slowly-relaxing, expanded GdmCl-denaturated state, ignoring the individuality of the different aminoacid side chain. The dynamics of the acid unfolded and molten globule state are similar in the framework of the Zimm model with internal friction, where the chains still interact and hinder each other: the first Zimm relaxation time is as large as the internal friction time. Transient formation of secondary structure elements in the acid unfolded and presence of α-helices in the molten globule state lead to internal friction to a similar extent.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2019

Reduced Internal Friction by Osmolyte Interaction in Intrinsically Disordered Myelin Basic Protein

Urea is a strong denaturing osmolyte that disrupts noncovalent bonds in proteins. Here, we present a small-angle neutron scattering (SANS) and neutron spin–echo spectroscopy (NSE) study on the structure and dynamics of the intrinsically disordered myelin basic protein (MBP) denatured by urea. SANS results show that urea-denatured MBP is more compact than ideal polymers, while its secondary structure content is entirely lost. Additionally, NSE experiments reveal concomitantly an increase of the relaxation time and of the amplitude of internal motions in urea-denatured MBP as compared to native MBP. If interpreted in terms of the Zimm model including internal friction (ZIF), the internal friction parameter decreased by a factor of 6.5. Urea seems to not only smooth local energy barriers, reducing internal friction on a local scale, but also significantly reduces the overall depth of the global energy landscape. This leads to a nearly complete loss of restoring forces beyond entropic forces and in turn allows for larger motional amplitudes. Obviously, the noncovalent H-bonds are largely eliminated, driving the unfolded protein to be more similar to a synthetic polymer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗