Crystal Structure of the Staphylococcus aureus pI258 CadC Cd(II)/Pb(II)/Zn(II)-Responsive Repressor

The Staphylococcus aureus plasmid pI258 cadCA operon encodes a P-type ATPase, CadA, that confers resistance to the heavy metals Cd(II), Zn(II), and Pb(II). Expression of this heavy-metal efflux pump is regulated by CadC, a homodimeric repressor that dissociates from the cad operator/promoter upon binding of Cd(II), Pb(II), or Zn(II). CadC is a member of the ArsR/SmtB family of metalloregulatory proteins. Here we report the X-ray crystal structure of CadC at 1.9 Å resolution. The dimensions of the protein dimer are approximately 30 Å by 40 Å by 70 Å. Each monomer contains six α-helices and a three-stranded β-sheet. Helices 4 and 5 form a classic helix-turn-helix motif that is the putative DNA binding region. The α1 helix of one monomer crosses the dimer to approach the α4 helix of the other monomer, consistent with the previous proposal that these two regulatory metal binding sites for the inducer cadmium or lead are each formed by Cys-7 and Cys-11 from the N terminus of one monomer and Cys-58 and Cys-60 of the other monomer. Two nonregulatory metal binding sites containing zinc are formed between the two antiparallel α6 helices at the dimerization interface. This is the first reported three-dimensional structure of a member of the ArsR/SmtB family with regulatory metal binding sites at the DNA binding domain and the first structure of a transcription repressor that responds to the heavy metals Cd(II) and Pb(II)

A Novel Iron(II) Preferring Dopamine Agonist Chelator as Potential Symptomatic and Neuroprotective Therapeutic Agent for Parkinson’s Disease

Parkinson’s disease (PD) is a progressive neurodegenerative disorder, and development of disease-modifying treatment is still an unmet medical need. Considering the implication of free iron­(II) in PD, we report here the design and characterization of a novel hybrid iron chelator, (−)-<b>12</b> (D-607) as a multitarget-directed ligand against PD. Binding and functional assays at dopamine D₂/D₃ receptors indicate potent agonist activity of (−)-<b>12</b>. The molecule displayed an efficient preferential iron­(II) chelation properties along with potent in vivo activity in a reserpinized PD animal model. The compound also rescued PC12 cells from toxicity induced by iron delivered intracellularly in a dose-dependent manner. However, Fe³⁺ selective dopamine agonist 1 and a well-known antiparkinsonian drug pramipexole produced little to no neuroprotection effect under the same experimental condition. These observations strongly suggest that (−)-<b>12</b> should be a promising multifunctional lead molecule for a viable symptomatic and disease modifying therapy of PD

What Does a KAP Survey Reveal about the Awareness Regarding Leishmaniasis among the Community of an Endemic Area in Sri Lanka?

Leishmaniasis is one of the neglected tropical diseases. Studies show that the poor knowledge about epidemiological aspects of leishmaniasis within communities causes the collapse of existing disease control programs. Therefore, the present study focuses on a detailed survey of the existing awareness among the threatened population in the Medawachchiya Public Health Inspector’s (PHI) Area in the Anuradhapura District, Sri Lanka, aiming to assist the health staff to organize community-based vector control programs effectively in the future. Assessment of the awareness of residents of two hundred and seventy households (n = 270) from 10 Grama Niladhari Divisions (GNDs) was carried out by using a structured questionnaire. Among 143 females and 134 males, only 75.1% had knowledge about the disease, 5.8% (n = 16) of the participants knew only about the vector, and 28.9% (n = 80) knew about control methods. The study showed a considerable lack of awareness about the disease among the studied population. The study found that age and education levels had significant impacts on knowledge, attitudes, and practices. However, factors like gender, marital status, occupation, income, and expenses did not show significant correlations. The present study suggests huge scope for greater achievements in community-related vector control methods by implementing a continuous educational program

A Novel Iron(II) Preferring Dopamine Agonist Chelator as Potential Symptomatic and Neuroprotective Therapeutic Agent for Parkinson’s Disease

Parkinson’s disease (PD) is a progressive neurodegenerative disorder, and development of disease-modifying treatment is still an unmet medical need. Considering the implication of free iron­(II) in PD, we report here the design and characterization of a novel hybrid iron chelator, (−)-<b>12</b> (D-607) as a multitarget-directed ligand against PD. Binding and functional assays at dopamine D₂/D₃ receptors indicate potent agonist activity of (−)-<b>12</b>. The molecule displayed an efficient preferential iron­(II) chelation properties along with potent in vivo activity in a reserpinized PD animal model. The compound also rescued PC12 cells from toxicity induced by iron delivered intracellularly in a dose-dependent manner. However, Fe³⁺ selective dopamine agonist 1 and a well-known antiparkinsonian drug pramipexole produced little to no neuroprotection effect under the same experimental condition. These observations strongly suggest that (−)-<b>12</b> should be a promising multifunctional lead molecule for a viable symptomatic and disease modifying therapy of PD

Biochemical Characterization of ArsI: A Novel C–As Lyase for Degradation of Environmental Organoarsenicals

Organoarsenicals such as the methylarsenical methylarsenate (MAs­(V)) and aromatic arsenicals including roxarsone (4-hydroxy-3-nitrobenzenearsenate or Rox­(V)) have been extensively used as an herbicide and growth enhancers in animal husbandry, respectively. They undergo environmental degradation to more toxic inorganic arsenite (As­(III)) that contaminates crops and drinking water. We previously identified a bacterial gene (<i>arsI</i>) responsible for aerobic demethylation of methylarsenite (MAs­(III)). The gene product, ArsI, is an Fe­(II)-dependent extradiol dioxygenase that cleaves the carbon–arsenic (C–As) bond in MAs­(III) and in trivalent aromatic arsenicals. The objective of this study was to elucidate the ArsI mechanism. Using isothermal titration calorimetry, we determined the dissociation constants and ligand-to-protein stoichiometry of ArsI for Fe­(II), MAs­(III), and aromatic phenylarsenite. Using a combination of methods including chemical modification, site-directed mutagenesis, and fluorescent spectroscopy, we demonstrated that amino acid residues predicted to participate in Fe­(II)-binding (His5–His62–Glu115) and substrate binding (Cys96–Cys97) are involved in catalysis. Finally, the products of Rox­(III) degradation were identified as As­(III) and 2-nitrohydroquinone, demonstrating that ArsI is a dioxygenase that incorporates one oxygen atom from dioxygen into the carbon and the other to the arsenic to catalyze cleavage of the C–As bond. These results augment our understanding of the mechanism of this novel C–As lyase