Biology subjects

Stransky, J.

Publications and source records attributed to Stransky, J..

2 recordsLinked to original sources

bioRxiv2024

Structural and functional characterization of SidF, a possible dual substrate Aspergillus fumigatus N5-acetyl-N5-hydroxy-L-ornithine transacetylase

Siderophore-mediated iron acquisition is essential for the virulence of Aspergillus fumigatus, a fungus causing life-threatening aspergillosis. Developing drugs targeting the siderophore biosynthetic pathway could help improve disease management. The transacetylases SidF and SidL generate intermediates for different siderophores in A. fumigatus. A. fumigatus has a yet unidentified transacetylase that complements SidL during iron deficiency in SidL-lacking mutants. We present the first X-ray structure of SidF, revealing a conserved two-domain architecture with tetrameric assembly. Importantly, the N-terminal domain contributes to protein solubility and oligomerization, while the C-terminal domain containing the GCN5-related N-acetyltransferase (GNAT) motif is crucial for the enzymatic activity and mediates oligomer formation. Notably, AlphaFold modelling demonstrated structural similarity between SidF and SidL. Enzymatic assays showed that SidF can utilize acetyl-CoA as a donor, previously thought to be a substrate of SidL but not SidF, and selectively uses N5-hydroxy-L-ornithine as an acceptor. Based on these findings, we propose SidF as the unknown transacetylase complementing SidL activity, highlighting its central role in A. fumigatus siderophore biosynthesis. This study elucidates the structure of SidF and reveals a novel role in siderophore biosynthesis. Investigation of this uncharacterized GNAT protein enhances our understanding of fungal virulence and holds promise for its potential application in developing antifungal therapies.

biochemistry↗

bioRxiv2021

Crystal structure of the human NKR-P1 bound to its lymphocyte ligand LLT1 reveals receptor clustering in the immune synapse

Human NKR-P1 (CD161, KLRB1) and its ligand LLT1 (CLEC2D) are a prototypical inhibitory C-type lectin-like receptor:ligand pair of NK cells with a critical role in homing lymphocytes to immune-privileged sites, particularly in multiple sclerosis, rheumatoid arthritis, and Crohns disease. Furthermore, NKR-P1:LLT1 inhibitory signaling is associated with glioblastoma, non-Hodgkins lymphoma, breast, and prostate cancer. However, the lack of structural data on the formation of the NKR-P1:LLT1 complex limits our understanding of this signaling. We thus solved the crystal structures of NKR-P1 and the NKR-P1:LLT1 complex. NKR-P1 forms a homodimer with an unexpected arrangement that enables LLT1 binding in two modes, bridging two LLT1 molecules, thereby forming interaction clusters suggestive of an inhibitory immune synapse. Moreover, observing the formation of these clusters by SEC-SAXS analysis in solution and by dSTORM super-resolution microscopy on the cell surface, and following their role in receptor signaling using in vitro cytotoxicity assay with freshly isolated NK cells, we show how NKR-P1:LLT1 clustering allows these proteins to overcome the weak affinity of C-type lectin-like receptors to their ligands. Furthermore, only the ligation of both primary and secondary LLT1 binding interfaces leads to effective NKR-P1 inhibitory signaling. Therefore, our findings show how inhibitory receptor cross-linking and clustering work together to trigger signal transduction upon cellular contact in the immune synapse.

molecular biology↗