Novel DNA-Binding Activity Exhibited by Poly(aspartic acid) Hydrolase-1 Inhibits Poly(aspartic acid) Hydrolase Activity.

Significant attention has been shifted toward the use and development of biodegradable polymeric materials to mitigate environmental accumulation and potential health impacts. One such material, poly(aspartic acid) (PAA), is a biodegradable alternative to superabsorbent poly(carboxylates), like poly(acrylate). Three enzymes are known to hydrolyze PAA: PahZ1 and PahZ2 from sp.

Solvent-Dependent Emissions Properties of a Model Aurone Enable Use in Biological Applications.

Fluorophores are powerful visualization tools and the development of novel small organic fluorophores are in great demand. Small organic fluorophores have been derived from the aurone skeleton, 2-benzylidenebenzofuran-3(2H)-one. In this study, we have utilized a model aurone derivative with a methoxy group at the 3' position and a hydroxyl group at the 4' position, termed vanillin aurone, to develop a foundational understanding of structural factors impacting aurone fluorescence properties.

Risk Factors for Revision Surgery Following Revision Total Knee Arthroplasty Using a Hinged Knee Prosthesis for Septic and Aseptic Indications.

Introduction: The use of hinged knee replacements (HKRs) for limb salvage is a popular option for revision total knee arthroplasty (RTKA). Although recent literature focuses on the outcomes of HKR for septic and aseptic RTKAs, little is reported on the risk factors of returning to the operating room. The purpose of this study was to evaluate risk factors of revision surgery and revision after receiving HKR for septic versus aseptic etiology.

Aurone-derived 1,2,3-triazoles as potential fluorescence molecules .

Aurones are a class of well-studied natural compounds primarily responsible for the yellow pigment in flowering plants and have been shown to have fluorescent properties as well as beneficial biological effects. Traditionally, aurones can be easily synthesized through a Knoevenagel condensation of benzofuranones with arylaldehydes. Recently, Kafle unexpectedly synthesized a new aurone derivative containing a 1,2,3-triazole within its backbone.

A monomeric mycobacteriophage immunity repressor utilizes two domains to recognize an asymmetric DNA sequence.

Regulation of bacteriophage gene expression involves repressor proteins that bind and downregulate early lytic promoters. A large group of mycobacteriophages code for repressors that are unusual in also terminating transcription elongation at numerous binding sites (stoperators) distributed across the phage genome. Here we provide the X-ray crystal structure of a mycobacteriophage immunity repressor bound to DNA, which reveals the binding of a monomer to an asymmetric DNA sequence using two independent DNA binding domains.

Mini-Open Achilles Tendon Repair: Improving Outcomes While Decreasing Complications.

An acute rupture of the Achilles tendon is a traumatic injury that can cause considerable morbidity and reduced function. Nonoperative intervention may put patients at higher risk of rerupture, whereas surgical intervention carries risk of infection, wound complications, and iatrogenic nerve injury. The mini-open Achilles tendon repair technique has been popularized in helping decrease complications.

Engineered Sphingomonas sp. KT-1 PahZ1 monomers efficiently degrade poly(aspartic acid).

In recent years, there has been an effort toward creating and utilizing novel biodegradable polymeric materials. As products become available, it is necessary to concurrently search for novel biodegradation catalysts and further investigate the properties of known biodegradation enzymes. Regarding the latter, we recently reported the crystal structure of a dimeric enzyme, Sphingomonas sp.

sp. KT-1 PahZ2 Structure Reveals a Role for Conformational Dynamics in Peptide Bond Hydrolysis.

Poly(aspartic acid) (PAA) is a common water-soluble polycarboxylate used in a broad range of applications. PAA biodegradation and environmental assimilation were first identified in river water bacterial strains, sp. KT-1 and sp.

Hydrogen sulfide sensing using an aurone-based fluorescent probe.

Hydrogen sulfide detection and sensing is an area of interest from both an environmental and a biological perspective. While many methods are currently available, the most sensitive and biologically applicable ones are fluorescence based. In general, these fluorescent probes are based upon large, high-molecular weight, well-characterized fluorescent scaffolds that are synthetically demanding to prepare and difficult to tune and modify.

Examination of the Role of Mg in the Mechanism of Nucleotide Binding to the Monomeric YME1L AAA+ Domain.

The first line of defense in the mitochondrial quality control network involves the stress response from a family of ATP-dependent proteases. We have reported that a solubilized version of the mitochondrial inner membrane ATP-dependent protease YME1L displays nucleotide binding kinetics that are sensitive to the reactive oxygen species hydrogen peroxide under a limiting ATP concentration. Our observations were consistent with an altered YME1L conformational ensemble leading to increased nucleotide binding site accessibility under oxidative stress conditions.

Distally Unlocked Intramedullary Nailing With Cement Fixation for Impending and Actual Pathologic Humerus Fractures: A Retrospective Case Series.

Unlabelled: The humerus is a common site of metastatic tumor involvement and pathologic fracture. Intramedullary nailing is a treatment option that offers the benefit of protecting a long segment of diseased bone, but it is not without complications. This study aims to examine the survival, functional outcomes, and complications of patients treated with cement-augmented unlocked intramedullary nailing for actual and impending pathologic fractures of the humeral shaft.

Fluorescence Methods Applied to the Description of Urea-Dependent YME1L Protease Unfolding.

ATP-dependent proteases are ubiquitous across all kingdoms of life and are critical to the maintenance of intracellular protein quality control. The enzymatic function of these enzymes requires structural stability under conditions that may drive instability and/or loss of function in potential protein substrates. Thus, these molecular machines must demonstrate greater stability than their substrates in order to ensure continued function in essential quality control networks.

Characterization of Mitochondrial YME1L Protease Oxidative Stress-Induced Conformational State.

Oxidative stress is a common challenge to mitochondrial function where reactive oxygen species are capable of significant organelle damage. The generation of mitochondrial reactive oxygen species occurs in the inner membrane and matrix compartments as a consequence of subunit function in the electron transport chain and citric acid cycle, respectively. Maintenance of mitochondrial proteostasis and stress response is facilitated by compartmentalized proteases that couple the energy of ATP hydrolysis to unfolding and the regulated removal of damaged, misfolded, or aggregated proteins.

ClpC1 N-Terminal Domain Is Dispensable for Adaptor Protein-Dependent Allosteric Regulation.

ClpC1 hexamers couple the energy of ATP hydrolysis to unfold and, subsequently, translocate specific protein substrates into the associated ClpP protease. Substrate recognition by ATPases associated with various cellular activities (AAA+) proteases is driven by the ATPase component, which selectively determines protein substrates to be degraded. The specificity of these unfoldases for protein substrates is often controlled by an adaptor protein with examples that include MecA regulation of ClpC or ClpS-mediated control of ClpA.

Phylogenetic analysis predicts structural divergence for proteobacterial ClpC proteins.

Regulated proteolysis is required in all organisms for the removal of misfolded or degradation-tagged protein substrates in cellular quality control pathways. The molecular machines that catalyze this process are known as ATP-dependent proteases with examples that include ClpAP and ClpCP. Clp/Hsp100 subunits form ring-structures that couple the energy of ATP binding and hydrolysis to protein unfolding and subsequent translocation of denatured protein into the compartmentalized ClpP protease for degradation.

Fundamental Characteristics of AAA+ Protein Family Structure and Function.

Many complex cellular events depend on multiprotein complexes known as molecular machines to efficiently couple the energy derived from adenosine triphosphate hydrolysis to the generation of mechanical force. Members of the AAA+ ATPase superfamily (ATPases Associated with various cellular Activities) are critical components of many molecular machines. AAA+ proteins are defined by conserved modules that precisely position the active site elements of two adjacent subunits to catalyze ATP hydrolysis.

Archaeal MCM Proteins as an Analog for the Eukaryotic Mcm2-7 Helicase to Reveal Essential Features of Structure and Function.

In eukaryotes, the replicative helicase is the large multisubunit CMG complex consisting of the Mcm2-7 hexameric ring, Cdc45, and the tetrameric GINS complex. The Mcm2-7 ring assembles from six different, related proteins and forms the core of this complex. In archaea, a homologous MCM hexameric ring functions as the replicative helicase at the replication fork.

Escherichia coli ClpB is a non-processive polypeptide translocase.

Escherichia coli caseinolytic protease (Clp)B is a hexameric AAA+ [expanded superfamily of AAA (ATPase associated with various cellular activities)] enzyme that has the unique ability to catalyse protein disaggregation. Such enzymes are essential for proteome maintenance. Based on structural comparisons to homologous enzymes involved in ATP-dependent proteolysis and clever protein engineering strategies, it has been reported that ClpB translocates polypeptide through its axial channel.

Analysis of the crystal structure of an active MCM hexamer.

In a previous Research article (Froelich et al., 2014), we suggested an MCM helicase activation mechanism, but were limited in discussing the ATPase domain because it was absent from the crystal structure. Here we present the crystal structure of a nearly full-length MCM hexamer that is helicase-active and thus has all features essential for unwinding DNA.

ATPγS competes with ATP for binding at Domain 1 but not Domain 2 during ClpA catalyzed polypeptide translocation.

ClpAP is an ATP-dependent protease that assembles through the association of hexameric rings of ClpA with the cylindrically-shaped protease ClpP. ClpA contains two nucleotide binding domains, termed Domain 1 (D1) or 2 (D2). We have proposed that D1 or D2 limits the rate of ClpA catalyzed polypeptide translocation when ClpP is either absent or present, respectively.

E. coli ClpA catalyzed polypeptide translocation is allosterically controlled by the protease ClpP.

There are five known ATP-dependent proteases in Escherichia coli (Lon, ClpAP, ClpXP, HslUV, and the membrane-associated FtsH) that catalyze the removal of both misfolded and properly folded proteins in cellular protein quality control pathways. Hexameric ClpA rings associate with one or both faces of the cylindrically shaped tetradecameric ClpP protease. ClpA catalyzes unfolding and translocation of polypeptide substrates into the proteolytic core of ClpP for degradation through repeated cycles of ATP binding and hydrolysis at two nucleotide binding domains on each ClpA monomer.

Application of the sequential n-step kinetic mechanism to polypeptide translocases.

Clp/Hsp100 proteins are essential motor proteins in protein quality control pathways in all organisms. Such enzymes couple the energy derived from ATP binding and hydrolysis to translocate and unfold polypeptide substrates. Often they perform this role in collaboration with proteases for protein removal or with other chaperones for protein disaggregation.