Systematic mapping of the conformational landscape and dynamism of soluble fibrinogen

Impact of N-Glycosylation on Protein Structure and Dynamics Linked to Enzymatic C-H Activation in the M. oryzae Lipoxygenase

Lipoxygenases (LOXs) from pathogenic fungi are potential therapeutic targets for defense against plant and select human diseases. In contrast to the canonical LOXs in plants and animals, fungal LOXs are unique in having appended N-linked glycans. Such important post-translational modifications (PTMs) endow proteins with altered structure, stability, and/or function. In this study, we present the structural and functional outcomes of removing or altering these surface carbohydrates on the LOX from the devastating rice blast fungus, M. oryzae, MoLOX. Alteration of the PTMs did notinfluence the active site enzyme-substrate ground state structures as visualized by electron-nuclear double resonance (ENDOR) spectroscopy. However, removal of the eight N-linked glycans by asparagine-to-glutamine mutagenesis nonetheless led to a change in substrate selectivity and an elevated activation energy for the reaction with substrate linoleic acid, as determined by kinetic measurements. Comparative hydrogen-deuterium exchange mass spectrometry (HDX-MS) analysis of wild-type and Asn-to-Gln MoLOX variants revealed a regionally defined impact on the dynamics of the arched helix that covers the active site. Guided by these HDX results, a single glycan sequon knockout was generated at position 72, and its comparative substrate selectivity from kinetics nearly matched that of the Asn-to-Gln variant. The cumulative data from model glyco-enzyme MoLOX showcase how the presence, alteration, or removal of even a single N-linked glycan can influence the structural integrity and dynamics of the protein that are linked to an enzyme's catalytic proficiency, while indicating that extensive glycosylation protects the enzyme during pathogenesis by protecting it from protease degradation.

Integrating systemic immune-inflammation index, fibrinogen, and T-SPOT.TB for precision distinction of active pulmonary tuberculosis in the era of mycobacterial disease research

Background

The clinical challenge of differentiating suspected tuberculosis with positive T-SPOT.TB results persist. This study aims to investigate the utility of the Systemic Immune-Inflammation Index (SII), Fibrinogen, and T-SPOT.TB in distinguishing between active pulmonary tuberculosis (PTB) and non-tuberculous lung diseases.

Methods

A retrospective analysis included 1,327 cases of active PTB with positive T-SPOT.TB results and 703 cases of non-tuberculous lung diseases from May 2016 to December 2020 at Meizhou People's Hospital. These were designated as the case group and the control group, respectively. The detection indicators of T-SPOT.TB: Early Secreted Antigenic Target 6 (ESAT-6), Culture Filtrate Protein 10 (CFP-10), as well as SII and Fibrinogen levels-were compared and analyzed for association and joint diagnostic value between the two groups.

Results

The case group showed higher values of ESAT-6, CFP-10, SII, and Fibrinogen compared to the control group (all p < 0.001). In the case group, SII and Fibrinogen did not correlate with ESAT-6 and CFP-10 (∣rs∣ all < 0.3) but were positively correlated with C-reactive protein (CRP; rs all > 0.3). SII and Fibrinogen values in smear-positive pulmonary tuberculosis were higher than in smear-negative cases (all p < 0.05). The optimal diagnostic thresholds for ESAT-6, CFP-10, SII, and Fibrinogen in differentiating between active PTB and non-tuberculous lung diseases were 21.50 SFCs/106 PBMC, 22.50 SFCs/106 PBMC, 2128.32, and 5.02 g/L, respectively. Regression logistic analysis showed that ESAT-6 < 21.5 (OR: 1.637, 95% CI: 1.311-2.043, p < 0.001), CFP-10 < 22.5 (OR: 3.918, 95% CI: 3.138-4.892, p = 0.025), SII < 2128.32 (OR: 0.763, 95% CI: 0.603-0.967, p < 0.001), and FIB < 5.02 (OR: 2.287, 95% CI: 1.865-2.806, p < 0.001) were independent risk factors for active PTB. The specificity for ESAT-6 + CFP-10, ESAT-6 + CFP-10 + SII, ESAT-6 + CFP-10 + FIB, and ESAT-6 + CFP-10 + SII + FIB was 82.5%, 83.2%, 95.8%, and 80.1%, respectively, while sensitivity was 52.6%, 53.0%, 55.8%, and 44.7%, and positive predictive values were 85.0%, 85.6%, 84.1%, and 89.6%, respectively.

Conclusion

SII and Fibrinogen are positively correlated with the degree of tuberculosis inflammation and the bacterial load of Mycobacterium tuberculosis. The combined detection of SII, Fibrinogen, and T-SPOT.TB is significant in distinguishing between active PTB with positive T-SPOT.TB results and non-tuberculous lung diseases.

Interplay between intrinsic flexibility and sugar coating in Contactin-2 homodimerization

In this issue of Structure, Chataigner et al. reveal that Contactin-2's homotypic interaction, a glycosylation-dependent process, generates a broad conformational landscape. This structural plasticity, driven by conformational equilibria and sugar coating, facilitates adaptation to diverse ligands and environmental conditions, highlighting its dynamic role in neuronal function.

Fibrinogen and fibrin: synthesis, structure, and function in health and disease

Fibrinogen is an extraordinary molecule by any estimation. It is large, structurally intricate, and circulates at high concentrations. Its biological end product, insoluble fibrin(ogen) or fibrin, can assume a diverse array of conformations with the ability to interact with numerous plasma proteins and cells and withstand biochemical and biomechanical disruption to facilitate wound healing. Quantitative and qualitative defects in fibrinogen or fibrin are associated with bleeding, thrombosis, inflammation, and diseases affected by these processes. Numerous studies investigating mechanisms by which fibrin(ogen) and fibrin contribute to health and disease have been published. This review for the 20th-anniversary series in the Journal of Thrombosis and Haemostasis summarizes interesting aspects of fibrin(ogen) biology, biochemistry, biophysics, and physiology and highlights exciting findings published in the past 2 decades.