scholarly journals The C-terminal tail of the bacterial translocation ATPase SecA modulates its activity

2018 ◽  
Author(s):  
Mohammed Jamshad ◽  
Timothy J. Knowles ◽  
Scott A. White ◽  
Douglas G. Ward ◽  
Fiyaz Mohammed ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Metal Binding ◽  
Cytoplasmic Membrane ◽  
Protein Recognition ◽  
X Ray ◽  
Ribosome Binding ◽  
X Ray Crystallography ◽  
Substrate Protein ◽  
Metal Binding Domain

AbstractIn bacteria, the translocation of a subset of proteins across the cytoplasmic membrane by the Sec machinery requires SecA. Although SecA can recognise nascent polypeptides, the mechanism of cotranslational substrate protein recognition is not known. Here, we investigated the role of the C-terminal tail (CTT) of SecA, which consists of a flexible linker (FLD) and a small metal-binding domain (MBD), in its interaction with nascent polypeptides. Phylogenetic analysis and ribosome binding experiments indicated that the MBD interacts with 70S ribosomes. Disruption of the entire CTT or the MBD alone had opposing effects on ribosome binding, substrate-protein binding, ATPase activity and in vivo function. Autophotocrosslinking, mass spectrometry, x-ray crystallography and small-angle x-ray scattering experiments provided insight into the CTT-mediated conformational changes in SecA. Finally, photocrosslinking experiments indicated that binding of SecA to substrate protein affected its interaction with the ribosome. Taken together, our results suggest a mechanism for substrate protein recognition.Impact StatementSecA is an evolutionarily conserved ATPase that is required for the translocation of a subset of proteins across the cytoplasmic membrane in bacteria. We investigated how SecA recognises its substrate proteins at the ribosome as they are still being synthesised (i.e. cotranslationally).

scholarly journals The C-terminal tail of the bacterial translocation ATPase SecA modulates its activity

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Mohammed Jamshad ◽  
Timothy J Knowles ◽  
Scott A White ◽  
Douglas G Ward ◽  
Fiyaz Mohammed ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Metal Binding ◽  
Ribosome Binding ◽  
Substrate Protein ◽  
Metal Binding Domain ◽  
Opposing Effects ◽  
Substrate Proteins ◽  
Binding Substrate

In bacteria, the translocation of proteins across the cytoplasmic membrane by the Sec machinery requires the ATPase SecA. SecA binds ribosomes and recognises nascent substrate proteins, but the molecular mechanism of nascent substrate recognition is unknown. We investigated the role of the C-terminal tail (CTT) of SecA in nascent polypeptide recognition. The CTT consists of a flexible linker (FLD) and a small metal-binding domain (MBD). Phylogenetic analysis and ribosome binding experiments indicated that the MBD interacts with 70S ribosomes. Disruption of the MBD only or the entire CTT had opposing effects on ribosome binding, substrate-protein binding, ATPase activity and in vivo function, suggesting that the CTT influences the conformation of SecA. Site-specific crosslinking indicated that F399 in SecA contacts ribosomal protein uL29, and binding to nascent chains disrupts this interaction. Structural studies provided insight into the CTT-mediated conformational changes in SecA. Our results suggest a mechanism for nascent substrate protein recognition.

scholarly journals Iron is a ligand of SecA-like metal-binding domains in vivo

2020 ◽  
Vol 295 (21) ◽  
pp. 7516-7528
Author(s):  
Tamar Cranford-Smith ◽  
Mohammed Jamshad ◽  
Mark Jeeves ◽  
Rachael A. Chandler ◽  
Jack Yule ◽  
...  
Keyword(s):  
Sodium Azide ◽  
Metal Binding ◽  
Cytoplasmic Membrane ◽  
E Coli ◽  
Binding Domains ◽  
Equilibrium Binding ◽  
Plausible Model ◽  
Metal Binding Domain ◽  
Linker Domain

The ATPase SecA is an essential component of the bacterial Sec machinery, which transports proteins across the cytoplasmic membrane. Most SecA proteins contain a long C-terminal tail (CTT). In Escherichia coli, the CTT contains a structurally flexible linker domain and a small metal-binding domain (MBD). The MBD coordinates zinc via a conserved cysteine-containing motif and binds to SecB and ribosomes. In this study, we screened a high-density transposon library for mutants that affect the susceptibility of E. coli to sodium azide, which inhibits SecA-mediated translocation. Results from sequencing this library suggested that mutations removing the CTT make E. coli less susceptible to sodium azide at subinhibitory concentrations. Copurification experiments suggested that the MBD binds to iron and that azide disrupts iron binding. Azide also disrupted binding of SecA to membranes. Two other E. coli proteins that contain SecA-like MBDs, YecA and YchJ, also copurified with iron, and NMR spectroscopy experiments indicated that YecA binds iron via its MBD. Competition experiments and equilibrium binding measurements indicated that the SecA MBD binds preferentially to iron and that a conserved serine is required for this specificity. Finally, structural modeling suggested a plausible model for the octahedral coordination of iron. Taken together, our results suggest that SecA-like MBDs likely bind to iron in vivo.

scholarly journals Copper(I)-mediated protein–protein interactions result from suboptimal interaction surfaces

2009 ◽  
Vol 422 (1) ◽  
pp. 37-42 ◽  
Author(s):  
Lucia Banci ◽  
Ivano Bertini ◽  
Vito Calderone ◽  
Nunzia Della-Malva ◽  
Isabella C. Felli ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Metal Binding ◽  
Site Directed Mutagenesis ◽  
Protein Protein Interactions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Metal Binding Domain ◽  
Modelling Techniques ◽  
Cellular Pathways ◽  
P Type

The homoeostasis of metal ions in cells is the result of the contribution of several cellular pathways that involve transient, often weak, protein–protein interactions. Metal transfer typically implies the formation of adducts where the metal itself acts as a bridge between proteins, by co-ordinating residues of both interacting partners. In the present study we address the interaction between the human copper(I)-chaperone HAH1 (human ATX1 homologue) and a metal-binding domain in one of its partners, namely the P-type copper-transporting ATPase, ATP7A (ATPase, Cu+ transporting, α polypeptide). The adduct was structurally characterized in solution, in the presence of copper(I), and through X-ray crystallography, upon replacing copper(I) with cadmium(II). Further insight was obtained through molecular modelling techniques and site-directed mutagenesis. It was found that the interaction involves a relatively small interface (less than 1000 Å2, 1 Å=0.1 nm) with a low fraction of non-polar atoms. These observations provide a possible explanation for the low affinity of the two apoproteins. It appears that electrostatics is important in selecting which domain of the ATPase is able to form detectable amounts of the metal-mediated adduct with HAH1.

scholarly journals Cargo modulates the conformation of the nuclear pore in living cells

2020 ◽  
Author(s):  
Joan Pulupa ◽  
Harriet Prior ◽  
Daniel S. Johnson ◽  
Sanford M. Simon
Keyword(s):  
Conformational Changes ◽  
Nuclear Pore Complex ◽  
Conformational Dynamics ◽  
Living Cells ◽  
Nuclear Pore ◽  
Static Structure ◽  
X Ray ◽  
X Ray Crystallography

AbstractWhile the static structure of the nuclear pore complex (NPC) continues to be refined with cryo-EM and x-ray crystallography, the in vivo conformational dynamics of the NPC remain under-explored. We developed sensors that report on the orientation of NPC components by rigidly conjugating mEGFP to different NPC proteins. Our studies show conformational changes to select domains of Nups within the inner ring (Nup54, Nup58, Nup62) when transport through the NPC is perturbed and no conformational changes to Nups elsewhere in the NPC. Our results suggest that select components of the NPC are flexible and undergo conformational changes upon engaging with cargo.

scholarly journals Iron is a ligand of SecA-like metal-binding domains in vivo

2019 ◽  
Author(s):  
Tamar Cranford-Smith ◽  
Mohammed Jamshad ◽  
Mark Jeeves ◽  
Rachael A. Chandler ◽  
Jack Yule ◽  
...  
Keyword(s):  
Sodium Azide ◽  
Metal Binding ◽  
Cytoplasmic Membrane ◽  
E Coli ◽  
Binding Domains ◽  
Equilibrium Binding ◽  
Plausible Model ◽  
Metal Binding Domain ◽  
Linker Domain

ABSTRACTThe ATPase SecA is an essential component of the bacterial Sec machinery, which transports proteins across the cytoplasmic membrane. Most SecA proteins contain a long C-terminal tail (CTT). In Escherichia coli, the CTT contains a structurally flexible linker domain and a small metal-binding domain (MBD). The MBD coordinates zinc via a conserved cysteine-containing motif and binds to SecB and ribosomes. In this study, we screened a high-density transposon library for mutants that affect the susceptibility of E. coli to sodium azide, which inhibits SecA-mediated translocation. Results from sequencing this library suggested that mutations removing the CTT make E. coli less susceptible to sodium azide at subinhibitory concentrations. Copurification experiments suggested that the MBD binds to iron and that azide disrupts iron binding. Azide also disrupted binding of SecA to membranes. Two other E. coli proteins that contain SecA-like MBDs, YecA and YchJ, also copurified with iron, and NMR spectroscopy experiments indicated that YecA binds iron via its MBD. Competition experiments and equilibrium binding measurements indicated that the SecA MBD binds preferentially to iron and that a conserved serine is required for this specificity. Finally, structural modelling suggested a plausible model for the octahedral coordination of iron. Taken together, our results suggest that SecA-like MBDs likely bind to iron in vivo.

scholarly journals Conformation of the nuclear pore in living cells is modulated by transport state

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Joan Pulupa ◽  
Harriet Prior ◽  
Daniel S Johnson ◽  
Sanford M Simon
Keyword(s):  
Conformational Changes ◽  
Nuclear Pore Complex ◽  
Living Cells ◽  
Nuclear Pore ◽  
Static Structure ◽  
X Ray ◽  
X Ray Crystallography

While the static structure of the nuclear pore complex (NPC) continues to be refined with cryo-EM and x-ray crystallography, in vivo conformational changes of the NPC remain under-explored. We developed sensors that report on the orientation of NPC components by rigidly conjugating mEGFP to different NPC proteins. Our studies show conformational changes to select domains of nucleoporins (Nups) within the inner ring (Nup54, Nup58, Nup62) when transport through the NPC is perturbed and no conformational changes to Nups elsewhere in the NPC. Our results suggest that select components of the NPC are flexible and undergo conformational changes upon engaging with cargo.

Tele-Substitution Reactions in the Synthesis of a Promising Class of Antimalarials

2020 ◽  
Author(s):  
Marat Korsik ◽  
Edwin Tse ◽  
David Smith ◽  
William Lewis ◽  
Peter J. Rutledge ◽  
...  
Keyword(s):  
Heterocyclic Ring ◽  
Ring System ◽  
Substitution Reactions ◽  
Laboratory Notebook ◽  
Polar Solvents ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Core ◽  
Nmr Data

<p></p><p>We have discovered and studied a <i>tele</i>substitution reaction in a biologically important heterocyclic ring system. Conditions that favour the <i>tele</i>-substitution pathway were identified: the use of increased equivalents of the nucleophile or decreased equivalents of base, or the use of softer nucleophiles, less polar solvents and larger halogens on the electrophile. Using results from X-ray crystallography and isotope labelling experiments a mechanism for this unusual transformation is proposed. We focused on this triazolopyrazine as it is the core structure of the <i>in vivo </i>active anti-plasmodium compounds of Series 4 of the Open Source Malaria consortium.</p> <p> </p> <p>Archive of the electronic laboratory notebook with the description of all conducted experiments and raw NMR data could be accessed via following link <a href="https://ses.library.usyd.edu.au/handle/2123/21890">https://ses.library.usyd.edu.au/handle/2123/21890</a> . For navigation between entries of laboratory notebook please use file "Strings for compounds in the article.pdf" that works as a reference between article codes and notebook codes, also this file contain SMILES for these compounds. </p><br><p></p>

scholarly journals Crystallographic and X-ray absorption spectroscopic characterization of Helicobacter pylori UreE bound to Ni2+ and Zn2+ reveals a role for the disordered C-terminal arm in metal trafficking

2012 ◽  
Vol 441 (3) ◽  
pp. 1017-1035 ◽  
Author(s):  
Katarzyna Banaszak ◽  
Vlad Martin-Diaconescu ◽  
Matteo Bellucci ◽  
Barbara Zambelli ◽  
Wojciech Rypniewski ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Metal Ions ◽  
Metal Binding ◽  
Metal Ion ◽  
Mutual Influence ◽  
Accurate Information ◽  
Metal Ion Binding ◽  
X Ray ◽  
X Ray Absorption

The survival and growth of the pathogen Helicobacter pylori in the gastric acidic environment is ensured by the activity of urease, an enzyme containing two essential Ni2+ ions in the active site. The metallo-chaperone UreE facilitates in vivo Ni2+ insertion into the apoenzyme. Crystals of apo-HpUreE (H. pylori UreE) and its Ni2+- and Zn2+-bound forms were obtained from protein solutions in the absence and presence of the metal ions. The crystal structures of the homodimeric protein, determined at 2.00 Å (apo), 1.59 Å (Ni2+) and 2.52 Å (Zn2+) resolution, show the conserved proximal and solvent-exposed His102 residues from two adjacent monomers invariably involved in metal binding. The C-terminal regions of the apoprotein are disordered in the crystal, but acquire significant ordering in the presence of the metal ions due to the binding of His152. The analysis of X-ray absorption spectral data obtained using solutions of Ni2+- and Zn2+-bound HpUreE provided accurate information of the metal-ion environment in the absence of solid-state effects. These results reveal the role of the histidine residues at the protein C-terminus in metal-ion binding, and the mutual influence of protein framework and metal-ion stereo-electronic properties in establishing co-ordination number and geometry leading to metal selectivity.

scholarly journals Unusual Conformational Changes in 6-Hydroxymethyl-7,8-dihydropterin Pyrophosphokinase as Revealed by X-ray Crystallography and NMR

2001 ◽  
Vol 276 (43) ◽  
pp. 40274-40281 ◽  
Author(s):  
Bing Xiao ◽  
Genbin Shi ◽  
Jinhai Gao ◽  
Jaroslaw Blaszczyk ◽  
Qin Liu ◽  
...  
Keyword(s):  
Conformational Changes ◽  
X Ray ◽  
X Ray Crystallography

scholarly journals Crystal structure of a pyridoxal 5′-phosphate-dependent aspartate racemase derived from the bivalve mollusc Scapharca broughtonii

2017 ◽  
Vol 73 (12) ◽  
pp. 651-656 ◽  
Author(s):  
Taichi Mizobuchi ◽  
Risako Nonaka ◽  
Motoki Yoshimura ◽  
Katsumasa Abe ◽  
Shouji Takahashi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Binding Site ◽  
Active Site ◽  
Metal Binding ◽  
Bivalve Mollusc ◽  
Active Site Residues ◽  
X Ray ◽  
Aspartate Racemase ◽  
Scapharca Broughtonii

Aspartate racemase (AspR) is a pyridoxal 5′-phosphate (PLP)-dependent enzyme that is responsible for D-aspartate biosynthesis in vivo. To the best of our knowledge, this is the first study to report an X-ray crystal structure of a PLP-dependent AspR, which was resolved at 1.90 Å resolution. The AspR derived from the bivalve mollusc Scapharca broughtonii (SbAspR) is a type II PLP-dependent enzyme that is similar to serine racemase (SR) in that SbAspR catalyzes both racemization and dehydration. Structural comparison of SbAspR and SR shows a similar arrangement of the active-site residues and nucleotide-binding site, but a different orientation of the metal-binding site. Superposition of the structures of SbAspR and of rat SR bound to the inhibitor malonate reveals that Arg140 recognizes the β-carboxyl group of the substrate aspartate in SbAspR. It is hypothesized that the aromatic proline interaction between the domains, which favours the closed form of SbAspR, influences the arrangement of Arg140 at the active site.

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