scholarly journals Structural Insights into the Mechanism of Four-Coordinate Cob(II)alamin Formation in the Active Site of theSalmonella entericaATP:Co(I)rrinoid Adenosyltransferase Enzyme: Critical Role of Residues Phe91 and Trp93

Biochemistry ◽  
2012 ◽  
Vol 51 (48) ◽  
pp. 9647-9657 ◽  
Author(s):  
Theodore C. Moore ◽  
Sean A. Newmister ◽  
Ivan Rayment ◽  
Jorge C. Escalante-Semerena
Keyword(s):  
Active Site ◽  
Critical Role ◽  
Structural Insights

Unveiling the critical role of active site interaction in single atom catalyst towards hydrogen evolution catalysis

Nano Energy ◽  
2022 ◽  
Vol 93 ◽  
pp. 106819
Author(s):  
Feng Li ◽  
Gao-Feng Han ◽  
Yunfei Bu ◽  
Shanshan Chen ◽  
Ishfaq Ahmad ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Active Site ◽  
Critical Role ◽  
Single Atom

scholarly journals Albino mutants of Streptomyces glaucescens tyrosinase

1991 ◽  
Vol 274 (3) ◽  
pp. 707-713 ◽  
Author(s):  
M P Jackman ◽  
A Hajnal ◽  
K Lerch
Keyword(s):  
Active Site ◽  
Critical Role ◽  
Site Directed Mutagenesis ◽  
Mutant Proteins ◽  
Carbonyl Derivatives ◽  
Hydrogen Bonding Interactions ◽  
Albino Phenotype ◽  
Derivatives Of ◽  
Streptomyces Glaucescens

Site-directed mutagenesis was used to determine the functional role of several residues of Streptomyces glaucescens tyrosinase. Replacement of His-37, -53, -193 or -215 by glutamine yields albino phenotypes, as determined by expression on melanin-indicator plates. The purified mutant proteins display no detectable oxy-enzyme and increased Cu lability at the binuclear active site. The carbonyl derivatives of H189Q and H193Q luminesce, with lambda max. displaced more than 25 nm to a longer wavelength compared with native tyrosinase. The remaining histidine mutants display no detectable luminescence. The results are consistent with these histidine residues (together with His-62 and His-189 reported earlier) acting as Cu ligands in the Streptomyces glaucescens enzyme. Conservative substitution of the invariant Asn-190 by glutamine also gives an albino phenotype, no detectable oxy-enzyme and labilization of active-site Cu. The luminescence spectrum of carbonyl-N190Q, however, closely resembles that of the native enzyme under conditions promoting double Cu occupancy of the catalytic site. A critical role for Asn-190 in active-site hydrogen-bonding interactions is proposed.

Structural insights into the peroxidase activity and inactivation of human peroxiredoxin 4

2011 ◽  
Vol 441 (1) ◽  
pp. 113-118 ◽  
Author(s):  
Xi Wang ◽  
Likun Wang ◽  
Xi'e Wang ◽  
Fei Sun ◽  
Chih-chen Wang
Keyword(s):  
Endoplasmic Reticulum ◽  
Structural Analysis ◽  
Conformational Changes ◽  
Active Site ◽  
High Reactivity ◽  
Structural Explanation ◽  
Disulfide Formation ◽  
Redox Forms ◽  
Structural Insights

Prx4 (peroxiredoxin 4) is the only peroxiredoxin located in the ER (endoplasmic reticulum) and a proposed scavenger for H2O2. In the present study, we solved crystal structures of human Prx4 in three different redox forms and characterized the reaction features of Prx4 with H2O2. Prx4 exhibits a toroid-shaped decamer constructed of five catalytic dimers. Structural analysis revealed conformational changes around helix α2 and the C-terminal reigon with a YF (Tyr-Phe) motif from the partner subunit, which are required for interchain disulfide formation between Cys87 and Cys208, a critical step of the catalysis. The structural explanation for the restricting role of the YF motif on the active site dynamics is provided in detail. Prx4 has a high reactivity with H2O2, but is susceptible to overoxidation and consequent inactivation by H2O2. Either deletion of the YF motif or dissociation into dimers decreased the susceptibility of Prx4 to overoxidation by increasing the flexibility of Cys87.

scholarly journals A Critical Role of Non-active Site Residues on Cyclooxygenase Helices 5 and 6 in the Control of Prostaglandin Stereochemistry at Carbon 15

2007 ◽  
Vol 282 (38) ◽  
pp. 28157-28163 ◽  
Author(s):  
Karin Valmsen ◽  
William E. Boeglin ◽  
Reet Järving ◽  
Ivar Järving ◽  
Külliki Varvas ◽  
...  
Keyword(s):  
Amino Acid ◽  
Active Site ◽  
Amino Acid Sequence Identity ◽  
Critical Role ◽  
Site Directed Mutagenesis ◽  
Single Amino Acid ◽  
Active Site Residues ◽  
The Core ◽  
The Difference

The correct stereochemistry of prostaglandins is a prerequisite of their biological activity and thus is under a strict enzymatic control. Recently, we cloned and characterized two cyclooxygenase (COX) isoforms in the coral Plexaura homomalla that share 97% amino acid sequence identity, yet form prostaglandins with opposite stereochemistry at carbon 15. The difference in oxygenation specificity is only partially accounted for by the single amino acid substitution in the active site (Ile or Val at position 349). For further elucidation of residues involved in the C-15 stereocontrol, a series of sequence swapping and site-directed mutagenesis experiments between 15R- and 15S-COX were performed. Our results show that the change in stereochemistry at carbon 15 of prostaglandins relates mainly to five amino acid substitutions on helices 5 and 6 of the coral COX. In COX proteins, these helices form a helix-turn-helix motif that traverses through the entire protein, contributing to the second shell of residues around the oxygenase active site; it constitutes the most highly conserved region where even slight changes result in loss of catalytic activity. The finding that this region is among the least conserved between the P. homomalla 15S- and 15R-specific COX further supports its significance in maintaining the desired prostaglandin stereochemistry at C-15. The results are particularly remarkable because, based on its strong conservation, the conserved middle of helix 5 is considered as central to the core structure of peroxidases, of which COX proteins are derivatives. Now we show that the same parts of the protein are involved in the control of oxygenation with 15R or 15S stereospecificity in the dioxygenase active site.

A Source of Response Regulator Autophosphatase Activity:  The Critical Role of a Residue Adjacent to the Spo0F Autophosphorylation Active Site†

Biochemistry ◽  
1998 ◽  
Vol 37 (21) ◽  
pp. 7725-7732 ◽  
Author(s):  
James Zapf ◽  
Madhusudan ◽  
Charles E. Grimshaw ◽  
James A. Hoch ◽  
Kottayil I. Varughese ◽  
...  
Keyword(s):  
Active Site ◽  
Response Regulator ◽  
Critical Role

scholarly journals Efficient ethanol oxidation by hemoglobin-capped gold nanoclusters: The critical role of Fe in the heme group as an oxophilic metal active site

2019 ◽  
Vol 103 ◽  
pp. 42-47 ◽  
Author(s):  
Morteza Sarparast ◽  
Fatemeh Molaabasi ◽  
Reza Ghazfar ◽  
Mona Maleka Ashtiani ◽  
Mohammad Balooch Qarai ◽  
...  
Keyword(s):  
Active Site ◽  
Ethanol Oxidation ◽  
Critical Role ◽  
Gold Nanoclusters ◽  
Heme Group

scholarly journals Dual role of strigolactone receptor signaling partner in inhibiting substrate hydrolysis

2021 ◽  
Author(s):  
Briana L Sobecks ◽  
Jiming Chen ◽  
Diwakar Shukla
Keyword(s):  
Active Site ◽  
Conformational Stability ◽  
Critical Role ◽  
Md Simulations ◽  
Binding Pocket ◽  
Conformational Ensemble ◽  
Downstream Signaling ◽  
F Box Protein ◽  
Substrate Hydrolysis

Plant branch and root growth relies on metabolism of the strigolactone (SL) hormone. The interaction between the SL molecule, Oryza sativa DWARF14 (D14) SL receptor, and D3 F-box protein has been shown to play a critical role in SL perception. Previously, it was believed that D3 only interacts with the closed form of D14 to induce downstream signaling, but recent experiments indicate that D3, as well as its C-terminal helix (CTH), can interact with the open form as well to inhibit strigolactone signaling. Two hypotheses for the CTH induced inhibition are that either the CTH affects the conformational ensemble of D14 by stabilizing catalytically inactive states, or the CTH interacts with SLs in a way that prevents them from entering the binding pocket. In this study, we have performed molecular dynamics (MD) simulations to assess the validity of these hypotheses. We used an apo system with only D14 and the CTH to test the active site conformational stability and a holo system with D14, the CTH, and an SL molecule to test the interaction between the SL and CTH. Our simulations show that the CTH affects both active site conformation and the ability of SLs to move into the binding pocket. In the apo system, the CTH allosterically stabilized catalytic residues into their inactive conformation. In the holo system, significant interactions between SLs and the CTH hindered the ability of SLs to enter the D14 binding pocket. These two mechanisms account for the observed decrease in SL binding to D14 and subsequent ligand hydrolysis in the presence of the CTH.

scholarly journals The active site histidines of creatine kinase. A critical role of His 61 situated on a flexible loop

1997 ◽  
Vol 6 (2) ◽  
pp. 331-339 ◽  
Author(s):  
Michael Forstner ◽  
Alexandre Müller ◽  
Martin Stolz ◽  
Theo Wallimann
Keyword(s):  
Creatine Kinase ◽  
Active Site ◽  
Critical Role ◽  
Flexible Loop ◽  
Kinase A
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