Tianjin University of Science and Technology

Cephalosporin C acylases (CCAs) catalyze the hydrolysis of cephalosporin C to 7-aminocephalosporanic acid, a key intermediate for semisynthetic cephalosporin antibiotics. The functional secretion of heterologous CCAs in Escherichia coli is often constrained by signal peptide efficiency. To enhance the production of the engineered CCA mutant A14 from Bosea sp. OK403, we performed systematic signal peptide screening and identified the native SP AsPGA as most effective. Following codon optimization to generate SP AsPGA∗ , targeted mutagenesis of its N-, H-, and C-regions produced the superior H9 mutant (C16A). This variant increased extracellular A14 expression and activity by 6.26-fold and 2.0-fold, respectively. Molecular dynamics simulations indicated the C16A substitution stabilizes the signal peptide conformation and facilitates SecA translocon interaction. This work establishes that systematic mining and engineering of signal peptides, particularly through mutations that enhance structural stability, is a powerful strategy for optimizing the secretory production of complex enzymes in recombinant systems. Strategy to enhance CPC acylase secretion in Escherichia coli via signal peptide mining, screening, and optimization, followed by structural analysis and molecular dynamics simulations of the resulting mutants.

Wide bandgap (WBG) perovskite plays an irreplaceable and critical role in tandem solar cells. However, the phase separation caused by excessively high halide content seriously restricts the performance and stability of the device. In this work, multifunctional regulation of the device was achieved by introducing 2,7-Dihydroxy-9-fluoronone (DHF) into both the top and bottom interfaces of the WBG perovskite. DHF achieved targeted passivation of the ionic defects in perovskite. In addition, the dual-interface energy level regulation not only enhanced hole extraction, but also enabled the conductivity type of perovskite to complete the transition from n-type to n+-type, thereby promoting electron transfer. Meanwhile, experiments showed that I- was more likely to migrate to the top interface with more defect sites, leading to phase separation, and DHF could effectively suppress phase separation. Density functional theory (DFT) indicated that the migration potential barrier for I- escaping from the surface of perovskite increases from 0.14 to 1.28eV. Finally, the device based on DHF dual interface modification achieved a photoelectric conversion efficiency (PCE) of 22.40%, maintaining 83% of the initial PCE after 1000h of AM 1.5 tracking and 88% of the initial PCE during 1000h of air stability.

Innate immune responses must be coordinated with the cellular metabolic state. The intracellular pattern recognition receptor NOD1 detects bacterial peptidoglycans and initiates signaling from cellular membranes, a process regulated by ZDHHC5-mediated palmitoylation. Using biochemical analyses and immune-competent cell models, we show that AMP-activated protein kinase (AMPK) integrates metabolic cues into NOD1 signaling by regulating ZDHHC5. AMPK phosphorylates ZDHHC5 at Ser296 and Ser380, weakens its association with Golga7B, and promotes its displacement from the plasma membrane, thereby reducing NOD1 palmitoylation, membrane localization, and downstream signaling. Conversely, stimulation with the NOD1 agonist C12-iE-DAP suppresses AMPK activity, stabilizing ZDHHC5 at the membrane and sustaining NOD1 activation. These findings define a reciprocal regulatory circuit linking metabolic stress sensing and innate immune signaling, and illustrate how metabolic pathways govern the spatial control of pattern recognition receptors in innate immunity.