Impact of Cardiolipin and Phosphatidylcholine Interactions on the Conformational Ensemble of Cytochrome c

Skin and soft tissue infection of Nontuberculous mycobacterium after injection lipolysis

BACKGROUND

Injection lipolysis is used for body and face contouring due to its minimal invasiveness and cost-effectiveness, but related complications such as nontuberculous mycobacterium infection significantly affect its clinical application.

AIMS

This study aimed to review the literature on NTM infection after injection lipolysis.

METHODS

We conducted a literature review of scientific journals published in Medline and PubMed up to September 2022 on patients with NTM skin and soft tissue infections. We used the keywords: nontuberculous mycobacterium, infection, injection lipolysis, and lipolytic solution in various combinations with the Boolean operators AND, OR, and NOT. Only articles available in English and full version publications were considered for this review. Here, we reviewed the relevant mechanisms and drugs for injectable lipolysis and analyzed the possible correlation between NTM infection and injection lipolysis. We also summarize methods for the diagnosis and treatment of NTM infections and present some perspectives on this therapy.

RESULTS

Many patients with NTM infections had a history of fat-related surgery or therapy. NTM infection after injection lipolysis may be related to inadequate disinfection and sterilization of injection equipment and clinical procedures, the unqualified medication itself and free fatty acids released during injection lipolysis. Currently, diagnosis and treatment of NTM infection after lipolysis injections remains challenging.

CONCLUSIONS

Injection lipolysis represents a helpful option for local fat reduction. Doctors should strictly abide by the aseptic operation standards and use qualified products for there is a correlation between skin and soft tissue infection of nontuberculous mycobacterium and injection lipolysis. Providers should understand the mechanism, indications, and associated risks of injection lipolysis when injecting fat-dissolving drugs to reduce localized fat.

NMR Reveals the Conformational Changes of Cytochrome C upon Interaction with Cardiolipin

Conformational change of cytochrome c (cyt c) caused by interaction with cardiolipin (CL) is an important step during apoptosis, but the underlying mechanism is controversial. To comprehensively clarify the structural transformations of cyt c upon interaction with CL and avoid the unpredictable alias that might come from protein labeling or mutations, the conformation of purified yeast iso–1 cyt c with natural isotopic abundance in different contents of CL was measured by using NMR spectroscopy, in which the trimethylated group of the protein was used as a natural probe. The data demonstrate that cyt c has two partially unfolded conformations when interacted with CL: one with Fe–His33 coordination and the other with a penta–coordination heme. The Fe–His33 coordination conformation can be converted into a penta–coordination heme conformation in high content of CL. The structure of cyt c becomes partially unfolded with more exposed heme upon interaction with CL, suggesting that cyt c prefers a high peroxidase activity state in the mitochondria, which, in turn, makes CL easy to be oxidized, and causes the release of cyt c into the cytoplasm as a trigger in apoptosis.

Subsecond Time-Resolved Mass Spectrometry in Dynamic Structural Biology

Life at the molecular level is a dynamic world, where the key players-proteins, oligonucleotides, lipids, and carbohydrates-are in a perpetual state of structural flux, shifting rapidly between local minima on their conformational free energy landscapes. The techniques of classical structural biology, X-ray crystallography, structural NMR, and cryo-electron microscopy (cryo-EM), while capable of extraordinary structural resolution, are innately ill-suited to characterize biomolecules in their dynamically active states. Subsecond time-resolved mass spectrometry (MS) provides a unique window into the dynamic world of biological macromolecules, offering the capacity to directly monitor biochemical processes and conformational shifts with a structural dimension provided by the electrospray charge-state distribution, ion mobility, covalent labeling, or hydrogen-deuterium exchange. Over the past two decades, this suite of techniques has provided important insights into the inherently dynamic processes that drive function and pathogenesis in biological macromolecules, including (mis)folding, complexation, aggregation, ligand binding, and enzyme catalysis, among others. This Review provides a comprehensive account of subsecond time-resolved MS and the advances it has enabled in dynamic structural biology, with an emphasis on insights into the dynamic drivers of protein function.

Conformational Dynamics of α-Synuclein during the Interaction with Phospholipid Nanodiscs by Millisecond Hydrogen-Deuterium Exchange Mass Spectrometry

Both normal and pathological functions of α-synuclein (αSN), an abundant protein in the central and peripheral nervous system, have been linked to its interaction with membrane lipid bilayers. The ability to characterize structural transitions of αSN upon membrane complexation will clarify molecular mechanisms associated with αSN-linked pathologies, including Parkinson's disease (PD), multiple systems atrophy, and other synucleinopathies. In this work, time-resolved electrospray ionization hydrogen/deuterium exchange mass spectrometry (TRESI-HDX-MS) was employed to acquire a detailed picture of αSN's conformational transitions as it undergoes complexation with nanodisc membrane mimics with different headgroup charges (zwitterionic DMPC and negative POPG). Using this approach, αSN interactions with DMPC nanodiscs were shown to be rapid exchanging and to have little impact on the αSN conformational ensemble. Interactions with nanodiscs containing lipids known to promote amyloidogenesis (e.g., POPG), on the other hand, were observed to induce substantial and specific changes in the αSN conformational ensemble. Ultimately, we identify a region corresponding residues 19-28 and 45-57 of the αSN sequence that is uniquely impacted by interactions with "amyloidogenic" lipid membranes, supporting the existing "broken-helix" model for α-synuclein/membrane interactions, but do not detect a "helical extension" that is also thought to play a role in αSN aggregation.

Scratching the surface: native mass spectrometry of peripheral membrane protein complexes

A growing number of integral membrane proteins have been shown to tune their activity by selectively interacting with specific lipids. The ability to regulate biological functions via lipid interactions extends to the diverse group of proteins that associate only peripherally with the lipid bilayer. However, the structural basis of these interactions remains challenging to study due to their transient and promiscuous nature. Recently, native mass spectrometry has come into focus as a new tool to investigate lipid interactions in membrane proteins. Here, we outline how the native MS strategies developed for integral membrane proteins can be applied to generate insights into the structure and function of peripheral membrane proteins. Specifically, native MS studies of proteins in complex with detergent-solubilized lipids, bound to lipid nanodiscs, and released from native-like lipid vesicles all shed new light on the role of lipid interactions. The unique ability of native MS to capture and interrogate protein–protein, protein–ligand, and protein–lipid interactions opens exciting new avenues for the study of peripheral membrane protein biology.

Insights on the Conformational Ensemble of Cyt C Reveal a Compact State during Peroxidase Activity

Cytochrome c (cyt c) is known for its role in the electron transport chain but transitions to a peroxidase-active state upon exposure to oxidative species. The peroxidase activity ultimately results in the release of cyt c into the cytosol for the engagement of apoptosis. The accumulation of oxidative modifications that accompany the onset of the peroxidase function are well-characterized. However, the concurrent structural and conformational transitions of cyt c remain undercharacterized. Fast photochemical oxidation of proteins (FPOP) coupled with mass spectrometry is a protein footprinting technique used to structurally characterize proteins. FPOP coupled with native ion mobility separation shows that exposure to H₂O₂ results in the accumulation of a compact state of cyt c. Subsequent top-down fragmentation to localize FPOP modifications reveals changes in heme coordination between conformers. A time-resolved functional assay suggests that this compact conformer is peroxidase active. Altogether, combining FPOP, ion mobility separation, and top-down and bottom-up mass spectrometry allows us to discern individual conformations in solution and obtain a better understanding of the conformational ensemble and structural transitions of cyt c as it transitions from a respiratory role to a proapoptotic role.