Biology subjects

Giller, K.

Publications and source records attributed to Giller, K..

4 recordsLinked to original sources

bioRxiv2026

A Heart Disease-Associated TSPO Variant Alters Transmembrane Helix Dynamics

The 18-kDa translocator protein TSPO is an outer mitochondrial membrane protein involved in cholesterol transport, stress response, and cellular metabolism. Although its five-helix architecture is conserved across species, the structural and dynamic features of human TSPO remain unresolved. Using solution NMR spectroscopy, we characterize the conformational dynamics of human TSPO in complex with a third-generation diagnostic ligand. We identify a dynamic N-terminal segment of the first transmembrane helix that does not form a stably populated helix but instead defines a flexible boundary between the cytosolic region and the transmembrane core. The common disease-associated A14V variant reduces this conformational heterogeneity by introducing short-range contacts and redistributing backbone dynamics across the protein. These changes preserve the overall fold while locally stabilizing the N-terminal transmembrane helix toward the VDAC interaction interface. Our findings reveal a human-specific dynamic architecture of TSPO and link variant-induced stabilization to modulation of transmembrane helix dynamics.

biophysics↗

bioRxiv2025

The clinical drug candidate anle138b binds predominantly to the central cavity in lipidic Aβ fibrils and modulates fibril formation.

Alzheimers disease is a specific neurodegenerative disorder, distinct from normal aging, with a growing unmet medical need. It is characterized by the accumulation of amyloid plaques in the brain, primarily consisting of amyloid beta (A{beta}) fibrils. Therapeutic antibodies can slow down the disease, but are associated with potential severe side effects, motivating the development of small molecules to halt disease progression. This study investigates the interaction between the clinical drug candidate small molecule anle138b and lipidic A{beta}40 fibrils of type 1 (L1). L1 fibrils were previously shown to closely resemble fibrils from Alzheimers patients18. Using high-resolution structural biology techniques, including cryo-electron microscopy (cryo-EM), nuclear magnetic resonance (NMR) spectroscopy enhanced by dynamic nuclear polarization (DNP), and molecular dynamics (MD) simulations, we find that anle138b selectively binds to a cavity within the fibril. This structural insight provides a deeper understanding of a potential drug-binding mechanism at the atomic level and may inform the development of novel therapies and diagnostic approaches. In addition, anle138b reduces fibril formation in the presence of lipids by approximately 75%. This may suggest a mechanistic connection to its previously reported activity in animal models of Alzheimers disease15.

biochemistry↗

bioRxiv2023

Cryo-EM structures of lipidic fibrils of amyloid-β (1-40)

Alzheimers disease (AD) is a progressive and incurable neurodegenerative disease characterized by the extracellular deposition of amyloid plaques. Investigation into the composition of these plaques revealed a high amount of amyloid-{beta} (A{beta}) fibrils and a high concentration of lipids, suggesting that fibril-lipid interactions may also be relevant for the pathogenesis of AD. Therefore, we grew A{beta}40 fibrils in the presence of lipid vesicles and determined their structure by cryo-electron microscopy (cryo-EM) to high resolution. The fold of the major polymorph is similar to the structure of brain-seeded fibrils reported previously. The majority of the lipids are bound to the fibrils as we show by cryo-EM and NMR spectroscopy. This apparent lipid extraction from vesicles observed here in vitro provides structural insights into potentially disease-relevant fibril-lipid interactions.

molecular biology↗

bioRxiv2023

Mechanism of sensor kinase CitA transmembrane signaling

Membrane bound histidine kinases (HKs) are ubiquitous sensors of extracellular stimuli in bacteria. Here, we used solid-state NMR in conjunction with crystallography, solution NMR and distance measurements to investigate the transmembrane signaling mechanism of a paradigmatic citrate sensing membrane embedded HK, CitA. Citrate binding in the sensory extracytoplasmic PAS domain (PASp) causes the linker to transmembrane helix 2 (TM2) to adopt a helical conformation. This triggers a piston-like pulling of TM2 and a quaternary structure rearrangement in the cytosolic PAS domain (PASc). Crystal structures of PASc reveal both anti-parallel and parallel dimer conformations. An anti-parallel to parallel transition upon citrate binding agrees with interdimer distances measured in the lipid embedded protein using a site-specific 19F label in PASc. These data show how Angstrom scale structural changes in the sensor domain are transmitted across the membrane to be converted and amplified into a nm scale shift in the linker to the phosphorylation subdomain of the kinase. One-Sentence SummaryTransmembrane signal transduction of a PAS-domain containing histidine kinase occurs via a piston-like pulling of a transmembrane helix, and amplification by cytoplasmic PAS domain dimer rearrangement.

molecular biology↗