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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]

Three 1-phenylindolin-2-one derivatives, namely 1-phenylindolin-2-one, C14H11NO, (I), 5-bromo-1-phenylindolin-2-one, C14H10BrNO, (II), and 5-iodo-1-phenylindolin-2-one, C14H10INO, (III), have been synthesized and their structures determined. Compounds (I) and (II) crystallized in the centrosymmetric space groups Pbca and P21/ c, respectively, while compound (III) crystallized in the polar space group Aea2. Density functional theory (DFT) calculations show that the molecular dipole moment gradually decreases in the order (I) > (II) > (III). The relatively smaller dipole moment of (III) and the larger non-electrostatic intermolecular interactions may be the main reasons for the noncentrosymmetric and polar structure of (III). [ABSTRACT FROM AUTHOR]

3-hydroxyacyl-CoA dehydrogenase (HAD, EC 1.1.1.35) is a homodimeric enzyme localized in the mitochondrial matrix, which catalyzes the third step in fatty acid β-oxidation. The crystal structures of human HAD and subsequent complexes with cofactor/substrate enabled better understanding of HAD catalytic mechanism. However, numerous human diseases were found related to mutations at HAD dimerization interface that is away from the catalytic pocket. The role of HAD dimerization in its catalytic activity needs to be elucidated. Here, we solved the crystal structure of Caenorhabditis elegans HAD (cHAD) that is highly conserved to human HAD. Even though the cHAD mutants (R204A, Y209A and R204A/Y209A) with attenuated interactions on the dimerization interface still maintain a dimerization form, their enzymatic activities significantly decrease compared to that of the wild type. Such reduced activities are in consistency with the reduced ratios of the catalytic intermediate formation. Further molecular dynamics simulations results reveal that the alteration of the dimerization interface will increase the fluctuation of a distal region (a.a. 60–80) that plays an important role in the substrate binding. The increased fluctuation decreases the stability of the catalytic intermediate formation, and therefore the enzymatic activity is attenuated. Our study reveals the molecular mechanism about the essential role of the HAD dimerization interface in its catalytic activity via allosteric effects. [ABSTRACT FROM AUTHOR]

C26H24N2NiO6, hexagonal, P6522 (no. 179), a = b = 11.0161(4) Å, c = 33.1459(8) Å, V = 3483.5(9) Å3, Z = 6, Rgt (F) = 0.0376, wRref (F2 ) = 0.0879, T = 295 K. [ABSTRACT FROM AUTHOR]

C26H24N2NiO6, hexagonal, P6522 (no. 179), a = b = 11.0161(4) Å, c = 33.1459(8) Å, V = 3483.5(9) Å3, Z = 6, Rgt (F) = 0.0376, wRref (F2 ) = 0.0879, T = 295 K. [ABSTRACT FROM AUTHOR]