X-ray Characterization of Conformational Changes of Human Apo- and Holo-Transferrin

Trace metals and astrocytes physiology and pathophysiology

Several trace metals, including iron, copper, manganese and zinc are essential for normal function of the nervous system. Both deficiency and excessive accumulation of these metals trigger neuropathological developments. The central nervous system (CNS) is in possession of dedicated homeostatic system that removes, accumulates, stores and releases these metals to fulfil nervous tissue demand. This system is mainly associated with astrocytes that act as dynamic reservoirs for trace metals, these being a part of a global system of CNS ionostasis. Here we overview physiological and pathophysiological aspects of astrocyte-cantered trace metals regulation.

Functional Flow Cytometry to Predict PD-L1 Conformational Changes

The programmed cell death protein 1/programmed cell death protein ligand 1 (PD-1/PD-L1) axis is one of the most widely recognized targets for cancer immunotherapy. Importantly, PD-L1 conformational changes can hinder target binding when living cells are used. Antibody affinity, equilibrium binding, association and dissociation rates, and other affinity-related constants are fundamental to ensure target saturation. Here, PD-L1 changes in conformation and their potential impact on PD-L1 function and mutation are explored. Specifically, we present detailed flow cytometry procedures to analyze PD-L1 reactivity in myeloid-derived suppressor cells (MDSCs). This approach can also be used to study the contribution of protein conformational changes in living cells. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Sample preparation for PD-L1+ myeloid-derived suppressor cells detection by flow cytometry Basic Protocol 2: Protocol preparation, sample acquisition, and gating strategy for flow cytometric screening of PD-L1+ myeloid-derived suppressor cells in patients with lung cancer Support Protocol 1: Bioinformatic tools for the analysis of flow cytometric data.

Imaging conformations of holo- and apo-transferrin on the single-molecule level by low-energy electron holography

Conformational changes play a key role in the biological function of many proteins, thereby sustaining a multitude of processes essential to life. Thus, the imaging of the conformational space of proteins exhibiting such conformational changes is of great interest. Low-energy electron holography (LEEH) in combination with native electrospray ion beam deposition (ES-IBD) has recently been demonstrated to be capable of exploring the conformational space of conformationally highly variable proteins on the single-molecule level. While the previously studied conformations were induced by changes in environment, it is of relevance to assess the performance of this imaging method when applied to protein conformations inherently tied to a function-related conformational change. We show that LEEH imaging can distinguish different conformations of transferrin, the major iron transport protein in many organisms, by resolving a nanometer-scale cleft in the structure of the iron-free molecule (apo-transferrin) resulting from the conformational change associated with the iron binding/release process. This, along with a statistical analysis of the data, which evidences a degree of flexibility of the molecules, indicates that LEEH is a viable technique for imaging function-related conformational changes in individual proteins.

Cisplatin Binding to Human Serum Transferrin: A Crystallographic Study

The molecular mechanism of how human serum transferrin (hTF) recognizes cisplatin at the atomic level is still unclear. Here, we report the molecular structure of the adduct formed upon the reaction of hTF with cisplatin. Pt binds the side chain of Met256 (at the N-lobe), without altering the protein overall conformation.