Enzyme mechanisms

  • Article
    | Open Access

    Photosynthetic Complex I (PS-CI) is proposed to couple ferredoxin oxidation and plastoquinone reduction to proton pumping across thylakoid membranes. Here the authors determine the reduction potentials of the iron-sulphur clusters of PS-CI and thus the bioenergetics of the electron transfer relay.

    • Katherine H. Richardson
    • , John J. Wright
    •  & Maxie M. Roessler
  • Article
    | Open Access

    The endoplasmic-reticulum aminopeptidase ERAP1 processes peptides for antigen presentation. Here, the authors assess ERAP1 conformational states in solution, providing insight into the molecular mechanisms of ERAP1 substrate-length dependent catalytic activity and regulation, including the effects of autoimmune disease-associated polymorphism.

    • Zachary Maben
    • , Richa Arya
    •  & Lawrence J. Stern
  • Article
    | Open Access

    Understanding the structure and dynamics of enzymes is important for a number of applications. Here, the authors report on the crystal structure of vanillic acid decarboxylase, and show how the dynamics of the UbiD superfamily enzymes relate to the covalent catalysis of aromatic (de)carboxylation.

    • Stephen A. Marshall
    • , Karl A. P. Payne
    •  & David Leys
  • Article
    | Open Access

    The link between gRNA sequence and Cas9 activity is well established but the mechanism underlying this relationship is not well understood. Here the authors show that gRNA sequence primarily influences activity by dictating the time it takes for Cas9 to find the target site in a species-specific manner.

    • E. A. Moreb
    •  & M. D. Lynch
  • Article
    | Open Access

    PARG and ARH3 are the main hydrolases to reverse serine poly(ADP-ribosylation) yet their activities in the process differ. Here, the authors synthesise linear and branched poly(ADP-ribose) molecules, perform structure-function analysis and elucidate the mechanistic differences between PARG and ARH3.

    • Johannes Gregor Matthias Rack
    • , Qiang Liu
    •  & Ivan Ahel
  • Article
    | Open Access

    The bacterial thymidylate synthase ThyX catalyzes the reductive methylation of deoxyuridylate (dUMP) into deoxythymidylate (dTMP) and requires both folate and flavin for activity. Here, the authors combine biochemical experiments, spectroscopic measurements and flavin synthesis chemistry to show that formaldehyde (CH2O) can replace the natural methylene donor of ThyX in a CH2O-shunt reaction, yielding a carbinolamine intermediate with the reduced flavin coenzyme, and they present the crystal structure of this intermediate.

    • Charles Bou-Nader
    • , Frederick W. Stull
    •  & Djemel Hamdane
  • Article
    | Open Access

    Many endoperoxide-containing natural products have been isolated, but the biosynthesis of the endoperoxides remains unclear. Here, the authors report the structural and functional analysis of the NvfI endoperoxidase that catalyzes the formation of fumigatonoid A in the biosynthesis of novofumigatonin, and show that it does not employ tyrosyl radical in the reaction.

    • Takahiro Mori
    • , Rui Zhai
    •  & Ikuro Abe
  • Article
    | Open Access

    The bacteriophytochrome DrBphP from Deinococcus radiodurans shows high sequence homology to the histidine kinase Agp1 from Agrobacterium fabrum but lacks kinase activity. Here, the authors structurally and biochemically analyse DrBphP and Agp1, showing that DrBphP is a light-activatable phosphatase.

    • Elina Multamäki
    • , Rahul Nanekar
    •  & Heikki Takala
  • Article
    | Open Access

    In Gram-positive bacteria, lipoprotein intramolecular transacylase Lit produces a lipoprotein variant with less immunogenicity. As such, Lit can be viewed as a virulence factor. Here, structural and functional characterization of the enzyme provides insight into its catalytic mechanism, setting the stage for future studies of Lit as a target for new antibiotics.

    • Samir Olatunji
    • , Katherine Bowen
    •  & Martin Caffrey
  • Article
    | Open Access

    Tapasin is part of the peptide loading complex necessary for presenting antigenic peptides on MHC-I for the induction of adaptive immunity. Here the authors show that tapasin interacts with MHC-I in both conserved and allele-specific regions to promote antigen presentation, with tapasin L18 and K16 residues both implicated in this molecular interaction.

    • Huan Lan
    • , Esam T. Abualrous
    •  & Christian Freund
  • Article
    | Open Access

    Prenylated indole alkaloids contain spirooxindole rings with a 3R or 3S carbon stereocenter, which determines their bioactivities, but the biocatalytic mechanism controlling the 3R- or 3S-spirooxindole formation was unclear. Here, the authors report the biochemical and structural characterization of the oxygenase/semipinacolase CtdE that catalyses the 3S-spirooxindole construction in the biosynthesis of 21R-citrinadin A.

    • Zhiwen Liu
    • , Fanglong Zhao
    •  & Xue Gao
  • Article
    | Open Access

    hNEIL1 (human endonuclease VIII-like 1) is a broadly specific DNA glycosylase for base excision repair. Here, the authors show that hNEIL1 can assume activated or triage conformations: the structural basis for the mechanism that enables broad specificity and reduces futile repair of normal bases.

    • Menghao Liu
    • , Jun Zhang
    •  & Chengqi Yi
  • Article
    | Open Access

    Gram-negative bacteria can display intrinsic antibiotic resistance due to the action of tripartite efflux pumps, which include a H+/drug antiporter component. Here, the authors present a structure-function analysis of antiporter AcrB in intermediate states of the transport cycle, showing novel drug-binding sites and transport pathways.

    • Heng-Keat Tam
    • , Wuen Ee Foong
    •  & Klaas M. Pos
  • Article
    | Open Access

    The chemical processes for the selective incorporation of deuterium into small molecules, of interest to organic and medicinal chemistry, are well established, while the enzymatic methods remain underdeveloped. Here, the authors use an enzymatic approach employing Chlorella variabilis NC64A photodecarboxylase that catalyses decarboxylative deuteration of various carboxylic acids with D2O, and identify enzyme variants that can employ substrates with different chain length acids.

    • Jian Xu
    • , Jiajie Fan
    •  & Qi Wu
  • Article
    | Open Access

    Enzyme reactions at interfaces are common in both Nature and industrial applications but no general kinetic framework exists for interfacial enzymes. Here, the authors kinetically characterize 83 cellulases and identify a scaling relationship between ligand binding strength and maximal turnover, a so-called linear free energy relationship, which may help rationalize cellulolytic mechanisms and guide the selection of technical enzymes.

    • Jeppe Kari
    • , Gustavo A. Molina
    •  & Peter Westh
  • Article
    | Open Access

    CAPPs are putative Primase-Polymerases associated with CRISPR-Cas operons. Here, the authors show CAPPs genetic and physical association with Cas1 and Cas2, their capacity to function as DNA-dependent DNA primases and DNA polymerases, and that Cas1-Cas2 complex adjacent to CAPP has bona fide spacer integration activity.

    • Katerina Zabrady
    • , Matej Zabrady
    •  & Aidan J. Doherty
  • Article
    | Open Access

    Substrate channeling can improve biosynthetic efficiency and has been implicated in the reactions of fusicoccadiene synthase. Here, the authors analyze this bifunctional enzyme complex by cryoEM, cross-linking MS and integrative modeling, providing structural insights into how substrate channeling is achieved.

    • Jacque L. Faylo
    • , Trevor van Eeuwen
    •  & David W. Christianson
  • Article
    | Open Access

    The activity of translation initiation factor eIF2B is known to be modulated through stress-responsive phosphorylation of its substrate eIF2. Here, the authors uncover the regulation of eIF2B by the binding of sugar phosphates, suggesting a link between nutrient status and the rate of protein synthesis.

    • Qi Hao
    • , Jin-Mi Heo
    •  & Carmela Sidrauski
  • Article
    | Open Access

    Clostridioides difficile adenine methyltransferase A (CamA) is required for the sporulation and colonization of the pathogen that causes gastrointestinal infections. Here, the authors characterise CamA kinetically and present its crystal structure bound to the DNA recognition sequence, which reveals DNA distortions including bending and the flipping of the target adenine out of the DNA helix, as well as protein conformational changes upon cofactor binding.

    • Jujun Zhou
    • , John R. Horton
    •  & Xiaodong Cheng
  • Article
    | Open Access

    DNA sequence preferences or statistical positioning of histones has not explained genomic patterns of nucleosome organisation in vivo. Here, the authors establish DNA shape/mechanics as key elements that have evolved together with binding sites of DNA sequence-specific barriers so that such information directs nucleosome positioning by chromatin remodelers.

    • Elisa Oberbeckmann
    • , Nils Krietenstein
    •  & Sebastian Eustermann
  • Article
    | Open Access

    Although chromatin remodelers have been shown to align nucleosome arrays to barriers and to generate spacing regularity among nucleosomes within arrays, it has remained unclear how the distance to barrier and the spacing length are determined in absolute terms. Here, the authors reveal that remodelers contain a ‘ruler’ element that sets remodeler-specific alignment and spacing distances when generating nucleosome arrays.

    • Elisa Oberbeckmann
    • , Vanessa Niebauer
    •  & Philipp Korber
  • Article
    | Open Access

    Caerulomycins and collismycins are two types of 2,2’-bipyridine natural products that are biosynthesized via a hybrid NRPS-PKS pathway, but the details of their biosynthesis were unknown. Here, the authors elucidate their biosynthetic pathways, validate the generality of 2,2’-bipyridine formation, and clarify the process for 2,2’-bipyridine furcation.

    • Bo Pang
    • , Rijing Liao
    •  & Wen Liu
  • Article
    | Open Access

    Type 2 DNA topoisomerases (Top2) regulates DNA topology during DNA replication, transcription, and chromosome segregation. Here the authors describe a complete structure of the catalytic core of the human Topo IIα bound to DNA and etoposide, providing insight into the regulation of Topo IIα activities and how opening of the DNA-gate is spatially connected to the ATPase domain.

    • Arnaud Vanden Broeck
    • , Christophe Lotz
    •  & Valérie Lamour
  • Article
    | Open Access

    Regulation of the MLL family of histone H3K4 methyltransferases on the nucleosome core particle (NCP) remains largely unknown. Here the authors show that intrinsically disordered regions of ASH2L and DPY30 restrict the rotational dynamics of MLL1 on the NCP, allowing more efficient enzyme-substrate engagement and higher H3K4 trimethylation activity.

    • Young-Tae Lee
    • , Alex Ayoub
    •  & Yali Dou
  • Article
    | Open Access

    Pinoresinol–lariciresinol reductases (PLRs) are enzymes involved in the lignan biosynthesis. Here, crystal structures of three PLRs in the apo, substrate-bound and product-bound states, and accompanying mutagenesis provide insight into PLRs catalytic mechanism and suggest a strategy for PLR engineering.

    • Ying Xiao
    • , Kai Shao
    •  & Wansheng Chen
  • Article
    | Open Access

    The allosteric regulation of the bienzyme complex imidazole glycerol phosphate synthase (HisFH) remains to be elucidated. Here, the authors provide structural insights into the dynamic allosteric mechanism by which ligand binding to the cyclase and glutaminase active sites of HisFH regulate enzyme activation.

    • Jan Philip Wurm
    • , Sihyun Sung
    •  & Remco Sprangers
  • Article
    | Open Access

    DNA polymerases are the key enzymes responsible for DNA replication and repair. Here the authors reveal through time-lapsed images of X-ray crystal structures that translocation precedes phosphodiester bond formation in the mechanism of DNA synthesis.

    • Nicholas Chim
    • , Roman A. Meza
    •  & John C. Chaput
  • Article
    | Open Access

    The MerR family of transcriptional regulators, such as EcmrR, activate promoters with a structure that is suboptimal for recognition by RNA polymerase holoenzyme. Structural insights into the EcmrR-dependent transcription process elucidate the mechanisms enabling optimal promoter recognition and transition from initiation to elongation.

    • Yang Yang
    • , Chang Liu
    •  & Bin Liu
  • Article
    | Open Access

    In some systems, a single protein comprising reverse transcriptase (RT), integrase and maturase enables concerted sequence integration and crRNA production. Here, analyses including the structure of a Cas6-RT-Cas1—Cas2 complex suggest coordination between all three active sites and capacity to acquire CRISPR sequences from RNA and DNA substrates.

    • Joy Y. Wang
    • , Christopher M. Hoel
    •  & Jennifer A. Doudna
  • Article
    | Open Access

    Non-ribosomal peptide synthetases (NRPSs) are multi-modular enzymes assembling complex natural products. Here, the structures of a Thermobifida fusca NRPS condensation domain bound to the substrate-bearing peptidyl carrier protein (PCP) domain provide insight into the mechanisms of substrate selectivity and engagement within the catalytic pocket.

    • Thierry Izoré
    • , Y. T. Candace Ho
    •  & Max J. Cryle
  • Article
    | Open Access

    The ER chaperone BiP is critical for the unfolded protein response and tightly regulated through reversible AMPylation by FICD, but the structural basis is unknown. Here the authors use thiol-reactive nucleotide derivatives to stabilize the transient FICD:BiP complex and determine its crystal structure.

    • Joel Fauser
    • , Burak Gulen
    •  & Aymelt Itzen
  • Article
    | Open Access

    The molecular mechanism of ubiquitin transfer from E1 to E2 enzymes is still unclear. By solving the crystal structure of a covalently trapped E1–E2–ubiquitin thioester mimetic, the authors identify two conformations of this complex which suggest an affinity switch mechanism for thioester transfer.

    • Lingmin Yuan
    • , Zongyang Lv
    •  & Shaun K. Olsen
  • Article
    | Open Access

    P450 oxidoreductase (POR) selectively activates numerous cytochromes P450 (CYP), crucial for metabolism of drugs, steroids and xenobiotics and natural product biosynthesis. Here, the authors identify ligands that bind POR and bias its specificity towards CYP redox partners, activating distinct metabolic cascades in cells.

    • Simon Bo Jensen
    • , Sara Thodberg
    •  & Nikos S. Hatzakis
  • Article
    | Open Access

    As part of two-component systems, diguanylate cyclases (DGCs) are activated by phosphorylation. Structural and computational analyses of DgcR, a model DGC, reveal the phosphorylation-induced conformational changes and the activation mechanism likely shared by many DGCs with N-terminal coiled-coil linkers.

    • Raphael D. Teixeira
    • , Fabian Holzschuh
    •  & Tilman Schirmer
  • Article
    | Open Access

    The glutamine fructose-6-phosphate amidotransferase 1 (GFAT-1) is the rate-limiting enzyme in the hexosamine pathway producing uridine 5’-diphospho-N-acetyl-D-glucosamine (UDP-GlcNAc), an essential glycosylation precursor. Here, the authors dissect the mechanisms of GFAT-1 regulation by protein kinase A (PKA)-mediated phosphorylation.

    • Sabine Ruegenberg
    • , Felix A. M. C. Mayr
    •  & Martin S. Denzel
  • Article
    | Open Access

    Human manganese superoxide dismutase (MnSOD) is an oxidoreductase that uses concerted proton and electron transfers to reduce the levels of superoxide radicals in mitochondria, but mechanistic insights into this process are limited. Here, the authors report neutron crystal structures of Mn3+SOD and Mn2+SOD, revealing changes in the protonation states of key residues in the enzyme active site during the redox cycle.

    • Jahaun Azadmanesh
    • , William E. Lutz
    •  & Gloria E. O. Borgstahl
  • Article
    | Open Access

    How DNA polymerases discriminate against oxidized and undamaged nucleotides during DNA repair is not fully understood. Here, the authors reveal high-resolution timelapse X-ray crystallography snapshots of DSB repair polymerase μ undergoing DNA synthesis providing mechanistic insights into the process.

    • Joonas A. Jamsen
    • , Akira Sassa
    •  & Samuel H. Wilson
  • Article
    | Open Access

    Microsomal glutathione S-transferase 2 (MGST2) produces leukotriene C4, an intracrine mediator of cell death. Structural, biochemical and computational analyses of human MGST2 suggest a mechanism employed by the enzyme to restrict catalysis to only one active site within the MGST2 trimer.

    • Madhuranayaki Thulasingam
    • , Laura Orellana
    •  & Jesper Z. Haeggström
  • Article
    | Open Access

    The phosphatidylinositol-3-phosphate (PI3P) is generated by the lipid kinase VPS34, in the context of VPS34 complex I on autophagosomes or complex II on endosomes. Biochemical and structural analyses provide insights into the mechanism of both VPS34 complexes recruitment to and activation on membranes by specific Rab GTPases.

    • Shirley Tremel
    • , Yohei Ohashi
    •  & Roger L. Williams
  • Article
    | Open Access

    The methylation of Histone 3 at Lysine 36 (H3K36) has been implicated in the regulation of transcription and coupled processes such as mRNA splicing. Here the authors show that the histone methyltransferase SETD2 interacts with hnRNP L to mediate the crosstalk between the transcription and splicing machineries.

    • Saikat Bhattacharya
    • , Michaella J. Levy
    •  & Jerry L. Workman
  • Article
    | Open Access

    Rubromycin family of natural products belongs to aromatic polyketides with diverse bioactivities, but details of their biosynthesis are limited. Here, the authors report the complete in vitro reconstitution of enzymatic formation of the spiroketal moiety of rubromycin polyketides, driven by flavin-dependent enzymes, and characterize reaction intermediates.

    • Britta Frensch
    • , Thorsten Lechtenberg
    •  & Robin Teufel
  • Article
    | Open Access

    2,5-Dihydroxypyridine dioxygenase NicX uses a mononuclear non-heme Fe(II) to catalyze the oxidative pyridine ring cleavage of the pollutant 2,5-hydroxypyridine. Here, the authors report crystal structures of NicX, identify residues involved in substrate stabilization and Fe(II) coordination, and propose the catalytic mechanism of NicX.

    • Gongquan Liu
    • , Yi-Lei Zhao
    •  & Ping Xu
  • Article
    | Open Access

    Exolytic heparinases are needed for sequencing of heparin and heparan sulfate (HP), but have not yet been reported. Here, the authors identify exolytic heparinases from different bacteria and show that the heparinases preferentially digest HP, determine the crystal structure of the exoheparinase BlexoHep and perform sequencing of HP octasaccharides using the enzyme.

    • Qingdong Zhang
    • , Hai-Yan Cao
    •  & Fuchuan Li