I24-Microfocus Macromolecular Crystallography
|
Jon
Agirre
,
Antonio
Ariza
,
Wendy
Offen
,
Johan
Turkenburg
,
Shirley
Roberts
,
Stuart
Mcnicholas
,
Paul V.
Harris
,
Brett
Mc Brayer
,
Jan
Dohnalek
,
Kevin
Cowtan
,
Gideon
Davies
,
Keith
Wilson
Diamond Proposal Number(s):
[1221]
Open Access
Abstract: The industrial conversion of cellulosic plant biomass into useful products such as biofuels is a major societal goal. These technologies harness diverse plant degrading enzymes, classical exo- and endo-acting cellulases and, increasingly, cellulose-active lytic polysaccharide monooxygenases, to deconstruct the recalcitrant β-D-linked polysaccharide. A major drawback with this process is that the exo-acting cellobiohydrolases suffer from severe inhibition from their cellobiose product. β-D-Glucosidases are therefore important for liberating glucose from cellobiose and thereby relieving limiting product inhibition. Here, the three-dimensional structures of two industrially important family GH3 β-D-glucosidases from Aspergillus fumigatus and A. oryzae, solved by molecular replacement and refined at 1.95 Å resolution, are reported. Both enzymes, which share 78% sequence identity, display a three-domain structure with the catalytic domain at the interface, as originally shown for barley β-D-glucan exohydrolase, the first three-dimensional structure solved from glycoside hydrolase family GH3. Both enzymes show extensive N-glycosylation, with only a few external sites being truncated to a single GlcNAc molecule. Those glycans N-linked to the core of the structure are identified purely as high-mannose trees, and establish multiple hydrogen bonds between their sugar components and adjacent protein side chains. The extensive glycans pose special problems for crystallographic refinement, and new techniques and protocols were developed especially for this work. These protocols ensured that all of the D-pyranosides in the glycosylation trees were modelled in the preferred minimum-energy 4C1 chair conformation and should be of general application to refinements of other crystal structures containing O- or N-glycosylation. The Aspergillus GH3 structures, in light of other recent three-dimensional structures, provide insight into fungal β-D-glucosidases and provide a platform on which to inform and inspire new generations of variant enzymes for industrial application.
|
Feb 2016
|
|
I04-Macromolecular Crystallography
|
Antonio
Ariza
,
Jens M.
Eklof
,
Oliver
Spadiut
,
Wendy A.
Offen
,
Shirley M.
Roberts
,
Werner
Besenmatter
,
Esben P.
Friis
,
Michael
Skjot
,
Keith S.
Wilson
,
Harry
Brumer
,
Gideon
Davies
Diamond Proposal Number(s):
[1221]
Open Access
Abstract: The enzymatic degradation of plant polysaccharides is emerging as one of the key environmental goals of the early 21st century, impacting on many processes in the textile and detergent industries as well as biomass conversion to biofuels. One of the well known problems with the use of nonstarch (nonfood)-based substrates such as the plant cell wall is that the cellulose fibers are embedded in a network of diverse polysaccharides, including xyloglucan, that renders access difficult. There is therefore increasing interest in the “accessory enzymes,” including xyloglucanases, that may aid biomass degradation through removal of “hemicellulose” polysaccharides. Here, we report the biochemical characterization of the endo-?-1,4-(xylo)glucan hydrolase from Paenibacillus polymyxa with polymeric, oligomeric, and defined chromogenic aryl-oligosaccharide substrates. The enzyme displays an unusual specificity on defined xyloglucan oligosaccharides, cleaving the XXXG-XXXG repeat into XXX and GXXXG. Kinetic analysis on defined oligosaccharides and on aryl-glycosides suggests that both the ?4 and +1 subsites show discrimination against xylose-appended glucosides. The three-dimensional structures of PpXG44 have been solved both in apo-form and as a series of ligand complexes that map the ?3 to ?1 and +1 to +5 subsites of the extended ligand binding cleft. Complex structures are consistent with partial intolerance of xylosides in the ?4? subsites. The atypical specificity of PpXG44 may thus find use in industrial processes involving xyloglucan degradation, such as biomass conversion, or in the emerging exciting applications of defined xyloglucans in food, pharmaceuticals, and cellulose fiber modification.
|
Sep 2011
|
|
I04-Macromolecular Crystallography
|
Antonio
Ariza
,
Olga
Moroz
,
Elena
Blagova
,
Johan
Turkenburg
,
Jitka
Waterman
,
Shirley
Roberts
,
Jesper
Vind
,
Carsten
Sjøholm
,
Søren F.
Lassen
,
Leonardo
De Maria
,
Vibe
Glitsoe
,
Lars K.
Skov
,
Keith
Wilson
Open Access
Abstract: Phytases hydrolyse phytate (myo-inositol hexakisphosphate), the principal form of phosphate stored in plant seeds to produce phosphate and lower phosphorylated myo-inositols. They are used extensively in the feed industry, and have been characterised biochemically and structurally with a number of structures in the PDB. They are divided into four distinct families: histidine acid phosphatases (HAP), β-propeller phytases, cysteine phosphatases and purple acid phosphatases and also split into three enzyme classes, the 3-, 5- and 6-phytases, depending on the position of the first phosphate in the inositol ring to be removed. We report identification, cloning, purification and 3D structures of 6-phytases from two bacteria, Hafnia alvei and Yersinia kristensenii, together with their pH optima, thermal stability, and degradation profiles for phytate. An important result is the structure of the H. alvei enzyme in complex with the substrate analogue myo-inositol hexakissulphate. In contrast to the only previous structure of a ligand-bound 6-phytase, where the 3-phosphate was unexpectedly in the catalytic site, in the H. alvei complex the expected scissile 6-phosphate (sulphate in the inhibitor) is placed in the catalytic site.
|
May 2013
|
|
I04-Macromolecular Crystallography
|
Alasdair R.
Gunn
,
Benito
Banos-pinero
,
Peggy
Paschke
,
Luis
Sanchez-pulido
,
Antonio
Ariza
,
Joseph
Day
,
Mehera
Emrich
,
David
Leys
,
Chris P.
Ponting
,
Ivan
Ahel
,
Nicholas D.
Lakin
Diamond Proposal Number(s):
[12346]
Open Access
Abstract: ADP-ribosylation by ADP-ribosyltransferases (ARTs) has a well-established role in DNA strand break repair by promoting enrichment of repair factors at damage sites through ADP-ribose interaction domains. Here we exploit the simple eukaryote Dictyostelium to uncover a role for ADP-ribosylation in regulating DNA interstrand crosslink repair and redundancy of this pathway with non-homologous end-joining (NHEJ). In silico searches identify a protein that contains a permutated macrodomain (Aprataxin/APLF-and-PNKP-Like protein; APL). Structural analysis reveals permutated macrodomains retain features associated with ADP-ribose interactions and APL is capable of binding poly-ADP-ribose through its macrodomain. APL is enriched in chromatin in response to cisplatin, an agent that induces DNA interstrand crosslinks (ICLs). This is dependent on the macrodomain of APL, and the ART Adprt2, indicating a role for ADP-ribosylation in the cellular response to cisplatin. Although adprt2(-) cells are sensitive to cisplatin, ADP-ribosylation is evident in these cells due to redundant signalling by the DSB-responsive ART Adprt1a, promoting NHEJ-mediated repair. These data implicate ADP-ribosylation in DNA ICL repair and identify NHEJ can function to resolve this form of DNA damage in the absence of Adprt2.
|
Oct 2016
|
|
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
|
Antonio
Ariza
,
Sian
Tanner
,
Cheryl T.
Walter
,
Kyle C.
Dent
,
Dale A.
Shepherd
,
Weining
Wu
,
Susan V.
Matthews
,
Julian A.
Hiscox
,
Todd J.
Green
,
Ming
Luo
,
Richard M.
Elliott
,
Anthony R.
Fooks
,
Alison E.
Ashcroft
,
Nicola J.
Stonehouse
,
Neil A.
Ranson
,
John N.
Barr
,
Thomas A.
Edwards
Open Access
Abstract: All orthobunyaviruses possess three genome segments of single-stranded negative sense RNA that are encapsidated with the virus-encoded nucleocapsid (N) protein to form a ribonucleoprotein (RNP) complex, which is uncharacterized at high resolution. We report the crystal structure of both the Bunyamwera virus (BUNV) N–RNA complex and the unbound Schmallenberg virus (SBV) N protein, at resolutions of 3.20 and 2.75 Å, respectively. Both N proteins crystallized as ring-like tetramers and exhibit a high degree of structural similarity despite classification into different orthobunyavirus serogroups. The structures represent a new RNA-binding protein fold. BUNV N possesses a positively charged groove into which RNA is deeply sequestered, with the bases facing away from the solvent. This location is highly inaccessible, implying that RNA polymerization and other critical base pairing events in the virus life cycle require RNP disassembly. Mutational analysis of N protein supports a correlation between structure and function. Comparison between these crystal structures and electron microscopy images of both soluble tetramers and authentic RNPs suggests the N protein does not bind RNA as a repeating monomer; thus, it represents a newly described architecture for bunyavirus RNP assembly, with implications for many other segmented negative-strand RNA viruses.
|
Apr 2013
|
|
I04-1-Macromolecular Crystallography (fixed wavelength)
|
Diamond Proposal Number(s):
[9306]
Open Access
Abstract: Poly(ADP-ribosyl)ation is a common post-translational modification that mediates a wide variety of cellular processes including DNA damage repair, chromatin regulation, transcription, and apoptosis. The difficulty associated with accessing poly(ADP-ribose) (PAR) in a homogeneous form has been an impediment to understanding the interactions of PAR with poly(ADP-ribose) glycohydrolase (PARG) and other binding proteins. Here we describe the chemical synthesis of the ADP-ribose dimer, and we use this compound to obtain the first human PARG substrate-enzyme cocrystal structure. Chemical synthesis of PAR is an attractive alternative to traditional enzymatic synthesis and fractionation, allowing access to products such as dimeric ADP-ribose, which has been detected but never isolated from natural sources. Additionally, we describe the synthesis of an alkynylated dimer and demonstrate that this compound can be used to synthesize PAR probes including biotin and fluorophore-labeled compounds. The fluorescently labeled ADP-ribose dimer was then utilized in a general fluorescence polarization-based PAR-protein binding assay. Finally, we use intermediates of our synthesis to access various PAR fragments, and evaluation of these compounds as substrates for PARG reveals the minimal features for substrate recognition and enzymatic cleavage. Homogeneous PAR oligomers and unnatural variants produced from chemical synthesis will allow for further detailed structural and biochemical studies on the interaction of PAR with its many protein binding partners.
|
Mar 2015
|
|
I04-1-Macromolecular Crystallography (fixed wavelength)
|
Diamond Proposal Number(s):
[1221]
Abstract: Glucoamylases are one of the most important classes of enzymes in the industrial degradation of starch biomass. They consist of a catalytic domain and a carbohydrate-binding domain (CBM), with the latter being important for the interaction with the polymeric substrate. Whereas the catalytic mechanisms and structures of the individual domains are well known, the spatial arrangement of the domains with respect to each other and its influence on activity are not fully understood. Here, the structures of three industrially used fungal glucoamylases, two of which are full length, have been crystallized and determined. It is shown for the first time that the relative orientation between the CBM and the catalytic domain is flexible, as they can adopt different orientations independently of ligand binding, suggesting a role as an anchor to increase the contact time and the relative concentration of substrate near the active site. The flexibility in the orientations of the two domains presented a considerable challenge for the crystallization of the enzymes.
|
May 2018
|
|
I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
|
Diamond Proposal Number(s):
[18069]
Open Access
Abstract: Protein ADP-ribosylation is a highly dynamic post-translational modification. The rapid turnover is achieved, among others, by ADP-(ribosyl)hydrolases (ARHs), an ancient family of enzymes that reverses this modification. Recently ARHs came into focus due to their role as regulators of cellular stresses and tumor suppressors. Here we present a comprehensive structural analysis of the enzymatically active family members ARH1 and ARH3. These two enzymes have very distinct substrate requirements. Our data show that binding of the adenosine ribose moiety is highly diverged between the two enzymes, whereas the active sites harboring the distal ribose closely resemble each other. Despite this apparent similarity, we elucidate the structural basis for the selective inhibition of ARH3 by the ADP-ribose analogues ADP-HPD and arginine-ADP-ribose. Together, our biochemical and structural work provides important insights into the mode of enzyme-ligand interaction, helps to understand differences in their catalytic behavior, and provides useful tools for targeted drug design.
|
Nov 2018
|
|
I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
|
Marcin J.
Suskiewicz
,
Florian
Zobel
,
Tom E. H.
Ogden
,
Pietro
Fontana
,
Antonio
Ariza
,
Ji-chun
Yang
,
Kang
Zhu
,
Lily
Bracken
,
William J.
Hawthorne
,
Dragana
Ahel
,
David
Neuhaus
,
Ivan
Ahel
Diamond Proposal Number(s):
[9306, 18069]
Abstract: The anti-cancer drug target poly(ADP-ribose) polymerase 1 (PARP1) and its close homologue, PARP2, are early responders to DNA damage in human cells1,2. Upon binding to genomic lesions, these enzymes utilise NAD+ to modify a plethora of proteins with mono- and poly(ADP-ribose) signals that are important for subsequent chromatin decompaction and repair factor recruitment3,4. These post-translational modification events are predominantly serine-linked and require HPF1, an accessory factor that is specific for the DNA damage response and switches the amino-acid specificity of PARP1/2 from aspartate/glutamate to serine residues5–10. Here, we report a co-structure of HPF1 bound to the catalytic domain of PARP2 that, in combination with NMR and biochemical data, reveals a composite active site formed by residues from both PARP1/2 and HPF1. We further show that the assembly of this new catalytic centre is essential for DNA damage-induced protein ADP-ribosylation in human cells. In response to DNA damage and NAD+ binding site occupancy, the HPF1–PARP1/2 interaction is enhanced via allosteric networks operating within PARP1/2, providing an additional level of regulation in DNA repair induction. As HPF1 forms a joint active site with PARP1/2, our data implicate HPF1 as an important determinant of the response to clinical PARP inhibitors.
|
Feb 2020
|
|
I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
|
Diamond Proposal Number(s):
[9306, 12346]
Open Access
Abstract: Strategies to resolve replication blocks are critical for the maintenance of genome stability. Among the factors implicated in the replication stress response is the ATP-dependent endonuclease ZRANB3. Here, we present the structure of the ZRANB3 HNH (His-Asn-His) endonuclease domain and provide a detailed analysis of its activity. We further define PCNA as a key regulator of ZRANB3 function, which recruits ZRANB3 to stalled replication forks and stimulates its endonuclease activity. Finally, we present the co-crystal structures of PCNA with two specific motifs in ZRANB3: the PIP box and the APIM motif. Our data provide important structural insights into the PCNA-APIM interaction, and reveal unexpected similarities between the PIP box and the APIM motif. We propose that PCNA and ATP-dependency serve as a multi-layered regulatory mechanism that modulates ZRANB3 activity at replication forks. Importantly, our findings allow us to interpret the functional significance of cancer associated ZRANB3 mutations.
|
Jun 2017
|
|
