Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 8 of 8
Full-Text Articles in Physics
Examination Of The Catalytic Role Of The Axial Cystine Ligand In The Co-Type Nitrile Hydratase From Pseudonocardia Thermophila Jcm 3095, Irene Anyango Ogutu, Martin St. Maurice, Brian Bennett, Richard C. Holz
Examination Of The Catalytic Role Of The Axial Cystine Ligand In The Co-Type Nitrile Hydratase From Pseudonocardia Thermophila Jcm 3095, Irene Anyango Ogutu, Martin St. Maurice, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
The strictly conserved αSer162 residue in the Co-type nitrile hydratase from Pseudonocardia thermophila JCM 3095 (PtNHase), which forms a hydrogen bond to the axial αCys108-S atom, was mutated into an Ala residue. The αSer162Ala yielded two different protein species: one was the apoform (αSerA) that exhibited no observable activity, and the second (αSerB) contained its full complement of cobalt ions and was active with a kcat value of 63 ± 3 s−1 towards acrylonitrile at pH 7.5. The X-ray crystal structure of was determined at 1.85 Å resolution and contained no detectable …
A Cobalt-Containing Eukaryotic Nitrile Hydratase, Salette Martinez, Xinhang Yang, Brian Bennett, Richard C. Holz
A Cobalt-Containing Eukaryotic Nitrile Hydratase, Salette Martinez, Xinhang Yang, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
Nitrile hydratase (NHase), an industrially important enzyme that catalyzes the hydration of nitriles to their corresponding amides, has only been characterized from prokaryotic microbes. The putative NHase from the eukaryotic unicellular choanoflagellate organism Monosiga brevicollis (MbNHase) was heterologously expressed in Escherichia coli. The resulting enzyme expressed as a single polypeptide with fused α- and β-subunits linked by a seventeen-histidine region. Size-exclusion chromatography indicated that MbNHase exists primarily as an (αβ)2 homodimer in solution, analogous to the α2β2 homotetramer architecture observed for prokaryotic NHases. The NHase enzyme contained its full complement of Co(III) …
Mutation Of H63 And Its Catalytic Affect On The Methionine Aminopeptidase From Escherichia Coli, Sanghamitra Mitra, Brian Bennett, Richard C. Holz
Mutation Of H63 And Its Catalytic Affect On The Methionine Aminopeptidase From Escherichia Coli, Sanghamitra Mitra, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
In order to gain insight into the mechanistic role of a flexible exterior loop near the active site, made up of Y62, H63, G64, and Y65, that has been proposed to play an important role in substrate binding and recognition in the methionyl aminopeptidase from Escherichia coli (EcMetAP-I), the H63A enzyme was prepared. Mutation of H63 to alanine does not affect the ability of the enzyme to bind divalent metal ions. The specific activity of H63A EcMetAP-I was determined using four different substrates of varying lengths, namely, l-Met-p-NA, MAS, MGMM and MSSHRWDW. For the smallest/shortest …
X-Ray Crystallographic Characterization Of The Co(Ii)-Substituted Tris-Bound Form Of The Aminopeptidase From Aeromonas Proteolytica, Petra Munih, Aaron Moulin, Carin Stamper, Brian Bennett, Dagmar Ringe, Gregory A. Petsko, Richard C. Holz
X-Ray Crystallographic Characterization Of The Co(Ii)-Substituted Tris-Bound Form Of The Aminopeptidase From Aeromonas Proteolytica, Petra Munih, Aaron Moulin, Carin Stamper, Brian Bennett, Dagmar Ringe, Gregory A. Petsko, Richard C. Holz
Physics Faculty Research and Publications
The X-ray crystal structure of the Co(II)-loaded form of the aminopeptidase from Aeromonas proteolytica ([CoCo(AAP)]) was solved to 2.2 Å resolution. [CoCo(AAP)] folds into an α/β globular domain with a twisted β-sheet hydrophobic core sandwiched between α-helices, identical to [ZnZn(AAP)]. Co(II) binding to AAP does not introduce any major conformational changes to the overall protein structure and the amino acid residues ligated to the dicobalt(II) cluster in [CoCo(AAP)] are the same as those in the native Zn(II)-loaded structure with only minor perturbations in bond lengths. The Co(II)–Co(II) distance is 3.3 Å. Tris(hydroxymethyl)aminomethane (Tris) coordinates to the dinuclear Co(II) active site …
Experimental Evidence For A Metallohydrolase Mechanism In Which The Nucleophile Is Not Delivered By A Metal Ion: Epr Spectrokinetic And Structural Studies Of Aminopeptidase From Vibrio Proteolyticus, Amit Kumar, Gopal R. Periyannan, Aaron W. Kittell, Jung Ja Kim, Brian Bennett
Experimental Evidence For A Metallohydrolase Mechanism In Which The Nucleophile Is Not Delivered By A Metal Ion: Epr Spectrokinetic And Structural Studies Of Aminopeptidase From Vibrio Proteolyticus, Amit Kumar, Gopal R. Periyannan, Aaron W. Kittell, Jung Ja Kim, Brian Bennett
Physics Faculty Research and Publications
Metallohydrolases catalyse some of the most important reactions in biology and are targets for numerous chemotherapeutic agents designed to combat bacterial infectivity, antibiotic resistance, HIV infectivity, tumour growth, angiogenesis and immune disorders. Rational design of inhibitors of these enzymes with chemotherapeutic potential relies on detailed knowledge of the catalytic mechanism. The roles of the catalytic transition ions in these enzymes have long been assumed to include the activation and delivery of a nucleophilic hydroxy moiety. In the present study, catalytic intermediates in the hydrolysis of L-leucyl-L-leucyl-L-leucine by Vibrio proteolyticus aminopeptidase were characterized in spectrokinetic and structural studies. Rapid-freeze-quench EPR studies …
Kinetic And Spectroscopic Characterization Of The E134a- And E134d-Altered Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase From Haemophilus Influenzae, Ryan S. Davis, David L. Bienvenue, Sabina I. Swierczek, Danuta M. Gilner, Lakshman Rajagopal, Brian Bennett, Richard C. Holz
Kinetic And Spectroscopic Characterization Of The E134a- And E134d-Altered Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase From Haemophilus Influenzae, Ryan S. Davis, David L. Bienvenue, Sabina I. Swierczek, Danuta M. Gilner, Lakshman Rajagopal, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
Glutamate-134 (E134) is proposed to act as the general acid/base during the hydrolysis reaction catalyzed by the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) from Haemophilus influenzae. To date, no direct evidence has been reported for the role of E134 during catalytic turnover by DapE. In order to elucidate the catalytic role of E134, altered DapE enzymes were prepared in which E134 was substituted with an alanine and an aspartate residue. The Michaelis constant (K m) does not change upon substitution with aspartate but the rate of the reaction changes drastically in the following order: glutamate (100% …
Characterization Of The Active Site And Insight Into The Binding Mode Of The Anti-Angiogenesis Agent Fumagillin To The Manganese(Ii)-Loaded Methionyl Aminopeptidase From Escherichia Coli, Ventris M. D'Souza, Robert S. Brown, Brian Bennett, Richard C. Holz
Characterization Of The Active Site And Insight Into The Binding Mode Of The Anti-Angiogenesis Agent Fumagillin To The Manganese(Ii)-Loaded Methionyl Aminopeptidase From Escherichia Coli, Ventris M. D'Souza, Robert S. Brown, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
EPR spectra were recorded for methionine aminopeptidase from Escherichia coli (EcMetAP-I) samples (~2.5 mM) to which one and two equivalents of Mn(II) were added (the latter is referred to as [MnMn(EcMetAP-I)]). The spectra for each sample were indistinguishable except that the spectrum of [MnMn(EcMetAP-I)] was twice as intense. The EPR spectrum of [MnMn(EcMetAP-I)] exhibited the characteristic six-line g≈2 EPR signal of mononuclear Mn(II) with A av(55Mn)=9.3 mT (93 G) and exhibited Curie-law temperature dependence. This signal is typical of Mn(II) in a ligand sphere comprising oxygen and/or nitrogen …
Inhibition Of The Aminopeptidase From Aeromonas Proteolytica By L-Leucinethiol: Kinetic And Spectroscopic Characterization Of A Slow, Tight-Binding Inhibitor–Enzyme Complex, David L. Bienvenue, Brian Bennett, Richard C. Holz
Inhibition Of The Aminopeptidase From Aeromonas Proteolytica By L-Leucinethiol: Kinetic And Spectroscopic Characterization Of A Slow, Tight-Binding Inhibitor–Enzyme Complex, David L. Bienvenue, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
The peptide inhibitor l-leucinethiol (LeuSH) was found to be a potent, slow-binding inhibitor of the aminopeptidase from Aeromonas proteolytica (AAP). The overall potency (KI*) of LeuSH was 7 nM while the corresponding alcohol l-leucinol (LeuOH) was a simple competitive inhibitor of much lower potency (KI=17 μM). These data suggest that the free thiol is likely involved in the formation of the E·I and E·I* complexes, presumably providing a metal ligand. In order to probe the nature of the interaction of LeuSH and LeuOH with the dinuclear active site of AAP, we have …