Search

Listeria monocytogenes, a food‐borne Gram‐positive pathogen, often causes diseases such as gastroenteritis, bacterial sepsis, and meningitis. Newly discovered extracellular electron transfer (EET) from L. monocytogenes plays critical roles in the generation of redox molecules as electron carriers in bacteria. A Mg2+‐dependent protein flavin mononucleotide (FMN) transferase (FmnB; UniProt: LMRG_02181) in EET is responsible for the transfer of electrons from intracellular to extracellular by hydrolyzing cofactor flavin adenine dinucleotide (FAD) and transferring FMN. FmnB homologs have been investigated in Gram‐negative bacteria but have been less well studied in Gram‐positive bacteria. In particular, the catalytic and inhibitory mechanisms of FmnB homologs remain elusive. Here, we report a series of crystal structures of apo‐FmnB and FmnB complexed with substrate FAD, three inhibitors AMP, ADP, and ATP, revealing the unusual catalytic triad center (Asp301‐Ser257‐His273) of FmnB. The three inhibitors indeed inhibited the activity of FmnB in varying degrees by occupying the binding site of the FAD substrate. The key residue Arg262 of FmnB was profoundly affected by ADP but not AMP or ATP. Overall, our studies not only provide insights into the promiscuous ligand recognition behavior of FmnB but also shed light on its catalytic and inhibitory mechanisms. [ABSTRACT FROM AUTHOR]

A novel zero‐dimensional dinuclear zinc complex, di‐μ‐acetato‐1:2κ4O:O′‐(μ‐2‐acetyl‐6‐{[(Z)‐2‐bromo‐3‐oxoprop‐1‐en‐1‐yl]azanidyl}phenolato‐1κ2O1,O2:2κ3O1,N,O6)(N,N‐dimethylacetamide‐1κO)dizinc(II), [Zn2(C11H8BrNO3)(CH3COO)2(C4H9NO)] or [Zn2(L)(CH3COO)2(DMA)], 1, was synthesized using (Z)‐3‐[(3‐acetyl‐2‐hydroxyphenyl)amino]‐2‐bromoprop‐2‐enal (H2L), which was synthesized from 1‐(3‐amino‐2‐hydroxyphenyl)ethanone and 2‐bromomalonaldehyde. H2L and 1 were characterized by single‐crystal X‐ray diffraction, FT–IR spectroscopy and elemental analysis. Theoretical calculations of the bond orders and excited state of H2L confirmed that there is extensive electron delocalization in the H2L molecules. Single‐crystal X‐ray diffraction shows that the two Zn atoms are pentacoordinated in distorted trigonal bipyramidal configurations in the crystals of 1. The thermogravimetric analysis of 1 shows that the main frame of the complex remains stable to about 190 °C. Powder X‐ray diffraction (PXRD) analysis shows that 1 possesses high purity and acid and alkali resistance. The intermolecular interactions of H2L and 1 were analyzed using Hirshfeld surface analysis and the results indicate that the H...H and O...H interactions of H2L and 1 play a considerable role in stabilizing the self‐assembly process. [ABSTRACT FROM AUTHOR]