Přírodovědecká fakultahttps://dspace.jcu.cz/handle/20.500.14390/417862026-04-15T07:53:50Z2026-04-15T07:53:50ZExciton Delocalization Promotes Far-Red Absorption in a Tetrameric Chlorophyll a Light-Harvesting Complex from Trachydiscus minutusSeki, SoichiroCupellini, LorenzoBína, DavidBetti, ElenaUrajová, PetraTanaka, HideakiMiyata, TomokoNamba, KeiichiKurisu, GenjiPolívka, TomášLitvín, RadekFujii, Ritsukohttps://dspace.jcu.cz/handle/20.500.14390/475502025-12-19T12:51:57Z2025-12-13T00:00:00ZExciton Delocalization Promotes Far-Red Absorption in a Tetrameric Chlorophyll a Light-Harvesting Complex from Trachydiscus minutus
Seki, Soichiro; Cupellini, Lorenzo; Bína, David; Betti, Elena; Urajová, Petra; Tanaka, Hideaki; Miyata, Tomoko; Namba, Keiichi; Kurisu, Genji; Polívka, Tomáš; Litvín, Radek; Fujii, Ritsuko
Photosynthetic organisms employ light-harvesting complexes (LHCs) to optimize energy capture under variable light conditions. The freshwater eustigmatophyte Trachydiscus minutus accumulates a red-shifted violaxanthin–chlorophyll protein (rVCP) that contributes to far-red light harvesting using only chlorophyll (Chl) a molecules, without chemical modification or substitution of pigments. Based on high-resolution cryo-EM and multiscale quantum chemical calculations, we uncovered a heterodimer-based tetrameric architecture, representing a unique oligomerization mode among LHCs. Within each heterodimer, Chls a are distinctively arranged adjacent to the terminal emitter, forming an unprecedentedly extended chlorophyll cluster. Quantum chemical calculations reveal three strong exciton-coupled pigment domains, two of which reside in the large cluster and solely account for the intense far-red absorption near 700 nm without contributions from charge–transfer states. Our structural and quantum chemical characterizations of far-red light harvesting reveal a molecular mechanism of red spectral tuning that relies on protein-controlled excitonic coupling of identical Chl a pigments, as demonstrated here in this eustigmatophyte, highlighting diverse adaptations for harvesting spectrally shifted, low-energy light.
2025-12-13T00:00:00ZAmblyostatin-1, the first salivary cystatin with host immunomodulatory and anti-inflammatory properties from the Neotropical tick Amblyomma sculptum, vector of Brazilian spotted feverMolari, Wilson SantosJmel, Mohamed AmineAssis, Josiane BetimFrazão-Silva, AlanBernardi, Julia MouraHuamanrayme, GrettaMedina, José MaríaEsteves, ElianeAntão, Solange CristinaCosta, Gabriel Cerqueira AlvesTanaka, Aparecida SadaeFogaca, Andréa CristinaFranta, ZdenekTirloni, LucasKotsyfakis, MichalisSá-Nunes, Andersonhttps://dspace.jcu.cz/handle/20.500.14390/475482025-11-18T10:24:39Z2025-07-17T00:00:00ZAmblyostatin-1, the first salivary cystatin with host immunomodulatory and anti-inflammatory properties from the Neotropical tick Amblyomma sculptum, vector of Brazilian spotted fever
Molari, Wilson Santos; Jmel, Mohamed Amine; Assis, Josiane Betim; Frazão-Silva, Alan; Bernardi, Julia Moura; Huamanrayme, Gretta; Medina, José María; Esteves, Eliane; Antão, Solange Cristina; Costa, Gabriel Cerqueira Alves; Tanaka, Aparecida Sadae; Fogaca, Andréa Cristina; Franta, Zdenek; Tirloni, Lucas; Kotsyfakis, Michalis; Sá-Nunes, Anderson
Introduction: The Neotropical tick Amblyomma sculptum is the primary vector
of Rickettsia rickettsii, the causative agent of Brazilian spotted fever, a disease
associated with high fatality rates. Tick saliva, a complex mixture of bioactive
molecules essential for successful blood feeding, facilitates pathogen
transmission and modulates host immune responses. A comprehensive
evaluation of the salivary gland transcriptome database reveals that protease
inhibitors are abundantly expressed molecules in tick saliva during feeding. Thus,
this study aims to describe and characterize the most expressed member of the
cystatin family identified in Amblyomma sculptum salivary transcriptome, named
Amblyostatin-1.
Methods: Bioinformatic tools were employed for in silico analysis of the
Amblyostatin-1 sequence and structure. A recombinant version of
Amblyostatin-1 was expressed in an Escherichia coli system, evaluated against
a panel of cysteine proteases in biochemical assays, and used to generate antibodies in immunized mice. The biological activities of Amblyostatin-1 were
assessed by its effects on dendritic cell maturation in vitro and in a carrageenaninduced
inflammation model in vivo.
Results: Based on its sequence and predicted three-dimensional structure,
Amblyostatin-1 is classified as an I25B cystatin, and its recombinant form
selectively inhibits cathepsins L, C, and S at different rates, with a low
nanomolar Ki value of 0.697 ± 0.22 nM against cathepsin L. Regarding its
biological activities, recombinant Amblyostatin-1 partially affects LPS-induced
dendritic cell maturation by downmodulating the costimulatory molecules CD80
and CD86 at higher micromolar concentrations (3 μM) while promoting IL-10
production at nanomolar concentrations (100 nM). The apparent lack of
Amblyostatin-1-specific antibody responses in immunized mice suggests an
impairment of antigen processing and presentation in vivo. Furthermore, in a
carrageenan-induced inflammation model, Amblyostatin-1 decreased edema
formation and neutrophil infiltration into the skin without affecting other
myeloid cells.
Discussion: These findings establish Amblyostatin-1 as a novel salivary cystatin
with immunomodulatory and anti-inflammatory properties, highlighting its
potential as an immunobiological agent.
2025-07-17T00:00:00Z