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1.
Complement Ther Med ; 26: 117-22, 2016 Jun.
Article in English | MEDLINE | ID: mdl-27261991

ABSTRACT

OBJECTIVE: To study dancers' perceptions of the physical, cognitive, affective, and social benefits of partnered dancing. METHOD: 225 dancers (71% female) were recruited through a community ballroom dance center and completed an online survey designed to measure their perceptions of the physical, cognitive, affective, and social benefits of modern, partnered dance styles (swing, Lindy Hop, and ballroom dancing). Subgroups were formed for analyses. For one set of analyses, groups based on length of dance participation were formed: experienced (dancing for more than 2 years) or novice (dancing for less than a year) dancers. For another set of analyses, groups based on frequency of dance practice were formed: committed (dancing at least one or more times per week) or occasional (dancing two or fewer times per month). RESULTS: The majority of participants reported perceived benefits in physical fitness, cognition, affect, and social functioning. Experienced dancers reported significantly greater self-perceived physical, social, and cognitive benefits than novice dancers. Committed dancers were more likely than occasional dancers to report improvements in physical fitness, U=6942, z=2.38, r=0.16, p<0.05. A Mann-Whitney test indicated that self-reported improvements in mood (i.e., feeling less depressed and more happy) were greater for women than for men, U=3945, z=-3.07, r=0.20, p<0.001. Length and frequency of dance participation significantly predicted perceived physical benefits [Χ(2) (1,6)=35.463, p <0.001, R(2)=0.16] and social benefits [Χ(2) (1,6)=15.776, p<0.05, R(2)=0.07], but not cognitive benefits. CONCLUSIONS: Results suggest that participation in partnered dance styles is associated with perceived improvements in physical fitness, cognitive functioning, social functioning, mood, and self-confidence, and that perceived benefits may increase as individuals dance more frequently and over longer periods of time.


Subject(s)
Dancing/physiology , Dancing/psychology , Health Knowledge, Attitudes, Practice , Adolescent , Adult , Female , Humans , Male , Middle Aged , Perception , Young Adult
2.
Nutr Metab Insights ; 8(Suppl 1): 57-77, 2015.
Article in English | MEDLINE | ID: mdl-27330305

ABSTRACT

Autism spectrum disorder (ASD) is characterized by social and communication impairments as well as by restricted, repetitive patterns of behavior and interests. Genomic studies have not revealed dominant genetic errors common to all forms of ASD. So ASD is assumed to be a complex disorder due to mutations in hundreds of common variants. Other theories argue that spontaneous DNA mutations and/or environmental factors contribute to as much as 50% of ASD. In reviewing potential genetic linkages between autism and alcoholism, it became apparent that all theories of ASD are consistent with aldehyde toxicity, in which endogenous and exogenous aldehydes accumulate as a consequence of mutations in key enzymes. Aldehyde toxicity is characterized by cell-localized, micronutrient deficiencies in sulfur-containing antioxidants, thiamine (B1), pyridoxine (B6), folate, Zn(2+), possibly Mg(2+), and retinoic acid, causing oxidative stress and a cascade of metabolic disturbances. Aldehydes also react with selective cytosolic and membrane proteins in the cell of origin; then some types migrate to damage neighboring cells. Reactive aldehydes also form adducts with DNA, selectively mutating bases and inducing strand breakage. This article reviews the relevant genomic, biochemical, and nutritional literature, which supports the central hypothesis that most ASD symptoms are consistent with symptoms of aldehyde toxicity. The hypothesis represents a paradigm shift in thinking and has profound implications for clinical detection, treatment, and even prevention of ASD. Insight is offered as to which neurologically afflicted children might successfully be treated with micronutrients and which children are unlikely to be helped. The aldehyde toxicity hypothesis likely applies to other neurological disorders.

3.
Protein Pept Lett ; 16(7): 834-41, 2009.
Article in English | MEDLINE | ID: mdl-19601915

ABSTRACT

The successful folding of a recombinant protein after expression and purification is essential for structural, biochemical and vaccination studies. Toxoplasma gondii recombinant GRA1 protein is a promising vaccine candidate against toxoplasmosis. In the present study, the folding of recombinant GRA1 protein has been evaluated by web based bioinformatics tools that predict protein folding. Subsequently, trypsin digestion, which is a simple indication of proper protein folding, has been used to determine whether recombinant GRA1 protein is likely to be folded. The results indicate that the recombinant GRA1 protein is predicted to be folded by most of the web based bioinformatics predictors. Moreover, in protease digestion experiments, the recombinant GRA1, which was purified to homogeneity without the use of denaturants, gives rise to a discrete band pattern that is indicative of a folded protein. Together, the results suggest that recombinant GRA1 protein is in a folded conformation, suitable for structural, biochemical and vaccination studies.


Subject(s)
Antigens, Protozoan/chemistry , Antigens, Protozoan/metabolism , Internet , Protein Folding , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Toxoplasma/chemistry , Trypsin/metabolism , Algorithms , Amino Acid Sequence , Animals , Antigens, Protozoan/isolation & purification , Computational Biology , Molecular Sequence Data , Recombinant Proteins/isolation & purification , Time Factors , Toxoplasma/genetics
4.
Mol Cancer Ther ; 8(2): 458-68, 2009 Feb.
Article in English | MEDLINE | ID: mdl-19174556

ABSTRACT

Epigenetic silencing of secreted wingless-type (Wnt) antagonists through hypermethylation is associated with tobacco smoking and with invasive bladder cancer. The secreted Wnt inhibitory factor-1 (WIF1) has shown consistent growth-inhibitory effect on various cancer cell lines. Therefore, we assessed the mechanisms of action of WIF1 by either restoring WIF1 expression in invasive bladder cancer cell lines (T24 and TSU-PR1) or using a recombinant protein containing functional WIF1 domain. Both ectopic expression of WIF1 and treatment with WIF1 domain protein resulted in cell growth inhibition via G(1) arrest. The G(1) arrest induced by WIF1 is associated with down-regulation of SKP2 and c-myc and up-regulation of p21/WAF1 and p27/Kip1. Conversely, reexpression of SKP2 in WIF1-overexpressing TSU-PR1 cells attenuated the WIF1-induced G(1) arrest. Furthermore, inhibition of nuclear Wnt signaling by either dominant-negative LEF1 or short hairpin RNA of TCF4 also reduced SKP2 expression. The human SKP2 gene contains two TCF/LEF1 consensus binding sites within the promoter. Chromatin immunoprecipitation/real-time PCR analysis revealed that both WIF1 and dominant-negative LEF1 expression decreased the in vivo binding of TCF4 and beta-catenin to the SKP2 promoter. Together, our results suggest that mechanisms of WIF1-induced G(1) arrest include (a) SKP2 down-regulation leading to p27/Kip1 accumulation and (b) c-myc down-regulation releasing p21/WAF1 transcription. Additionally, we show that WIF1 inhibits in vivo bladder tumor growth in nude mice. These observations suggest a mechanism for transformation of bladder epithelium on loss of WIF1 function and provide new targets such as SKP2 for intervention in WIF1-deficient bladder cancer.


Subject(s)
Adaptor Proteins, Signal Transducing/metabolism , G1 Phase , Proto-Oncogene Proteins c-myc/metabolism , Repressor Proteins/metabolism , S-Phase Kinase-Associated Proteins/metabolism , Urinary Bladder Neoplasms/pathology , Animals , Base Sequence , Cell Adhesion/drug effects , Cell Line, Tumor , Cell Nucleus/drug effects , Cell Nucleus/metabolism , Cell Proliferation/drug effects , Down-Regulation/drug effects , Gene Expression Regulation, Neoplastic/drug effects , Humans , Lymphoid Enhancer-Binding Factor 1/metabolism , Mice , Molecular Sequence Data , Neoplasm Invasiveness , Promoter Regions, Genetic , Protein Binding/drug effects , RNA, Messenger/genetics , RNA, Messenger/metabolism , RNA, Small Interfering/metabolism , Recombinant Proteins/pharmacology , S-Phase Kinase-Associated Proteins/genetics , Signal Transduction/drug effects , TCF Transcription Factors/metabolism , Transcription Factor 7-Like 2 Protein , Transcription, Genetic/drug effects , Urinary Bladder Neoplasms/genetics , Xenograft Model Antitumor Assays , beta Catenin/metabolism
5.
Altern Ther Health Med ; 14(3): 56-62, 2008.
Article in English | MEDLINE | ID: mdl-18517107

ABSTRACT

"Mauve Factor" was once mistaken for kryptopyrrole but is the hydroxylactam of hemopyrrole, hydroxyhemopyrrolin-2-one (HPL). Treatment with nutrients--particularly vitamin B6 and zinc--reduces urinary excretion of HPL and improves diverse neurobehavioral symptoms in subjects with elevated urinary HPL. Heightened HPL excretion classically associates with emotional stress, which in turn is known to associate with oxidative stress. For this review, markers for nutritional status and for oxidative stress were examined in relationship to urinary HPL. In cohorts with mixed diagnoses, 24-hour urinary HPL correlated negatively with vitamin B6 activity and zinc concentration in red cells (P < .0001). Above-normal HPL excretion corresponded to subnormal vitamin B6 activity and subnormal zinc with remarkable consistency. HPL correlated inversely with plasma GSH and red-cell catalase, and correlated directly with plasma nitric oxide (P < .0001). Thus, besides implying proportionate needs for vitamin B6 and zinc, HPL is a promising biomarker for oxidative stress. HPL is known to cause non-erythroid heme depression, which lowers zinc, increases nitric oxide, and increases oxidative stress. Administration of prednisone reportedly provoked HPL excretion in animals. Since adrenocorticoid (and catecholamine) stress hormones mediate intestinal permeability, urinary HPL was examined in relationship to urinary indicans, presumptive marker for intestinal permeability. Urinary HPL associated with higher levels ofindicans (P < .0001). Antibiotics reportedly reduce HPL in urine, suggesting an enterobic role in production. Potentially, gut is reservoir for HPL or its precursor, and stress-related changes in intestinal permeability mediate systemic and urinary concentrations.


Subject(s)
Free Radicals/metabolism , Nervous System Diseases/blood , Nervous System Diseases/urine , Pyrroles/blood , Pyrroles/urine , Antioxidants/therapeutic use , Heme Oxygenase (Decyclizing)/metabolism , Humans , Nervous System Diseases/therapy , Nutritional Status , Oxidation-Reduction , Oxidative Stress , Vitamin B 6/therapeutic use , Zinc/therapeutic use
6.
Altern Ther Health Med ; 14(2): 40-50, 2008.
Article in English | MEDLINE | ID: mdl-18383989

ABSTRACT

"Mauve Factor" was once mistaken for kryptopyrrole but is the hydroxylactam of hemopyrrole, hydroxyhemopyrrolin-2-one (HPL). Treatment with nutrients--particularly vitamin B6 and zinc--reduces urinary excretion of HPL and improves diverse neurobehavioral symptoms in subjects with elevated urinary HPL. Heightened HPL excretion classically associates with emotional stress, which in turn is known to associate with oxidative stress. For this review, markers for nutritional status and for oxidative stress were examined in relationship to urinary HPL. In cohorts with mixed diagnoses, 24-hour urinary HPL correlated negatively with vitamin B6 activity and zinc concentration in red cells (P < .0001). Above-normal HPL excretion corresponded to subnormal vitamin B6 activity and subnormal zinc with remarkable consistency. HPL correlated inversely with plasma glutathione and red-cell catalase, and correlated directly with plasma nitric oxide (P < .0001). Thus, besides implying proportionate needs for vitamin B6 and zinc, HPL is a promising biomarker for oxidative stress. HPL is known to cause non-erythroid heme depression, which lowers zinc, increases nitric oxide, and increases oxidative stress. Administration of prednisone reportedly provoked HPL excretion in animals. Since adrenocorticoid (and catecholamine) stress hormones mediate intestinal permeability, urinary HPL examined in relationship to urinary indicans, presumptive marker for intestinal permeability. Urinary HPL associated with higher levels of indicans (P < .0001). Antibiotics reportedly reduce HPL in urine, suggesting an enterobic role in production. Potentially, gut is a reservoir for HPL or its precursor, and stress-related changes in intestinal permeability mediate systemic and urinary concentrations.


Subject(s)
Free Radicals/metabolism , Nervous System Diseases/blood , Nervous System Diseases/urine , Pyrroles/blood , Pyrroles/urine , Antioxidants/therapeutic use , Heme Oxygenase (Decyclizing)/metabolism , Humans , Nervous System Diseases/therapy , Nutritional Status , Oxidation-Reduction , Oxidative Stress , Vitamin B 6/therapeutic use , Zinc/therapeutic use
7.
Oncol Rep ; 18(3): 691-4, 2007 Sep.
Article in English | MEDLINE | ID: mdl-17671721

ABSTRACT

Mutations in apc which lead to activation of the Wnt signaling pathway are a hallmark of sporadic colon cancers but occur infrequently in colon cancers arising in patients with inflammatory bowel disease (IBD). There is evidence, however, that other components of the Wnt pathway may be altered in IBD-related colon cancer. In this study, we examined the expression the Wnt pathway components frizzled (Fz), the cell surface receptor, and disheveled (DVL), a family of cytoplasmic signal transduction molecules, in IBD and IBD-related colon cancer. Paraffin sections of normal and malignant colon tissues were obtained from patients with a history of ulcerative colitis and from controls with sporadic colon cancer. Tissue sections were stained with antibodies directed against Fz1/2 receptors and DVL1, DVL2 and DVL3 and antigen expression visualized by immunohistochemistry. Fz1/2 receptors were minimally expressed in normal IBD mucosa, were not expressed in IBD colon cancer, but exhibited strong expression in dysplastic tissues adjacent to the cancers. DVL1 was not expressed in IBD normal mucosa or normal mucosa from non-IBD patients, but was expressed in all cancers. DVL2 and DVL3 were expressed in all normal mucosa samples tested, and in sporadic colon cancer, but were not expressed in colon cancers arising in IBD patients. The characteristics of Fz and DVL expression in IBD tissues reported herein provides evidence of the importance of Wnt signaling in IBD and IBD-related colon cancer and, specifically, the significance of non-APC components of this pathway. Fz may serve as a marker for dyspasia in IBD patients and DVL1 is a potential therapeutic target for IBD-related colon cancer.


Subject(s)
Colonic Neoplasms/genetics , Gene Expression Regulation, Neoplastic , Inflammatory Bowel Diseases/genetics , Wnt2 Protein/genetics , Colonic Neoplasms/pathology , Frizzled Receptors/genetics , Genes, APC , Humans , Inflammatory Bowel Diseases/complications , Inflammatory Bowel Diseases/pathology , Intestinal Mucosa/pathology , Intestinal Mucosa/physiology , Mutation , Receptors, G-Protein-Coupled/genetics , Reference Values
8.
Vaccine ; 25(10): 1824-37, 2007 Feb 26.
Article in English | MEDLINE | ID: mdl-17234306

ABSTRACT

The present study evaluates immunogenicity and protection potency of a codon-optimized GRA1 DNA vaccine, wild type GRA1 DNA vaccine and an adjuvanted recombinant GRA1 protein vaccine candidate in BALB/c mice against lethal toxoplasmosis. Of the three GRA1 vaccines tested, the recombinant GRA1 protein vaccine results reveal significant increase in immune response and prolonged survival against acute toxoplasmosis compared to DNA vaccinations. Immune response and protection conferred by codon-optimized GRA1 DNA vaccine was slightly better than wild type GRA1 DNA vaccine.


Subject(s)
Antigens, Protozoan/immunology , Toxoplasmosis/prevention & control , Vaccines, DNA/immunology , Vaccines, Subunit/immunology , Amino Acid Sequence , Animals , Antigens, Protozoan/genetics , Base Sequence , Disease Models, Animal , Female , Mice , Mice, Inbred BALB C , Molecular Sequence Data , Recombinant Proteins/immunology , Toxoplasmosis/immunology , Vaccines, DNA/genetics
9.
Acta Crystallogr D Biol Crystallogr ; 62(Pt 11): 1392-400, 2006 Nov.
Article in English | MEDLINE | ID: mdl-17057344

ABSTRACT

Two crystal forms of a complex between trypsin-modified elongation factor Tu-MgGDP from Escherichia coli and the antibiotic tetracycline have been solved by X-ray diffraction analysis to resolutions of 2.8 and 2.1 A, respectively. In the P2(1) form, cocrystals were grown from a solution mixture of the protein and tetracycline. Six copies of the trypsin-modified EF-Tu-MgGDP-tetracycline complex are arranged as three sets of dimers in the asymmetric unit. In the second crystal form, tetracycline was diffused into P4(3)2(1)2 crystals, resulting in a monomeric complex in the asymmetric unit. Atomic coordinates have been refined to crystallographic R factors of 18.0% for the P2(1) form and 20.0% for the P4(3)2(1)2 form. In both complexes, tetracycline makes significant interactions with the GTPase active site of EF-Tu. The phenoldiketone moiety of tetracycline interacts directly with the Mg(2+), the alpha-phosphate group of GDP and two amino acids, Thr25 and Asp80, which are conserved in the GX(4)GKS/T and DX(2)G sequence motifs found in all GTPases and many ATPases. The molecular complementarity, previously unrecognized between invariant groups present in all GTPase/ATPases and the active moiety of tetracycline, may have wide-ranging implications for all drugs containing the phenoldiketone moiety as well as for the design of new compounds targeted against a broad range of GTPases or ATPases.


Subject(s)
Escherichia coli Proteins/chemistry , Escherichia coli/chemistry , Peptide Elongation Factor Tu/chemistry , Tetracycline/chemistry , Binding Sites , Crystallography, X-Ray/methods , Escherichia coli/metabolism , Escherichia coli Proteins/metabolism , Guanosine Diphosphate/chemistry , Guanosine Diphosphate/metabolism , Peptide Elongation Factor Tu/metabolism , Protein Binding , Protein Structure, Quaternary , Protein Structure, Secondary , Tetracycline/metabolism
10.
Acta Crystallogr D Biol Crystallogr ; 62(Pt 4): 433-8, 2006 Apr.
Article in English | MEDLINE | ID: mdl-16552145

ABSTRACT

Escherichia coli elongation factor Tu-GDP (EF-Tu-GDP) was crystallized in the presence of novel inhibitors. The only crystals which could be grown were epitaxially as well as merohedrally twinned, highly mosaic and diffracted to a resolution of 3.4 A in space group P3(1)21, with unit-cell parameters a = b = 69.55, c = 169.44 A, alpha = beta = 90, gamma = 120 degrees . To determine whether an inhibitor was present in the crystal, a poor-quality X-ray diffraction data set had to be processed. The three-dimensional structure was ultimately solved and the original question answered. The results also reveal a new type of dimer packing for EF-Tu-GDP.


Subject(s)
Escherichia coli/chemistry , Peptide Elongation Factor Tu/chemistry , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/metabolism , Binding Sites , Crystallization , Crystallography, X-Ray , Dimerization , Guanosine Diphosphate/chemistry , Magnesium/chemistry , Models, Molecular , Peptide Elongation Factor Tu/metabolism , Protein Binding , Protein Structure, Tertiary
11.
Mol Cancer Ther ; 4(12): 1923-35, 2005 Dec.
Article in English | MEDLINE | ID: mdl-16373707

ABSTRACT

Apurinic/apyrimidinic endonuclease-1/redox factor-1 (APE/Ref-1) is a multifunctional protein involved in DNA base excision repair and redox regulation of many transcription factors. In different melanoma cell lines, we found that both nucleus and cytoplasm exhibited higher levels of Ref-1 compared with normal melanocytes. Similar increases of Ref-1 expression, detected by immunohistofluorescence, were also evident in nevi and malignant melanoma biopsies compared with normal skin, which were predominantly localized in the nucleus. Using recombinant adenovirus Adref-1, encoding full-length Ref-1, we transiently overexpressed APE/Ref-1 in human melanocytes, which protected these cells from UVB-induced apoptosis and increased foci formation in culture. Ref-1 overexpression also protected melanoma cells from cisplatin- or H2O2-induced apoptosis, whereas increased apoptosis was observed with Ref-1 antisense construct infection. These observations suggested that intracellular Ref-1 levels played an important role in sensitization of melanoma cells to apoptosis. Electrophoretic mobility shift assay results showed that in both cultured primary and metastatic melanomas DNA-binding activities of activator protein-1 and nuclear factor-kappaB were significantly diminished or shifted when anti-APE/Ref-1 antibody was added to deplete APE/Ref-1 from the binding complexes. Induced nuclear factor-kappaB transcriptional activities were also evident after Ref-1 overexpression. Furthermore, using three-dimensional molecular structure modeling and virtual screening, we found that resveratrol, a natural compound found in fruits and vegetables, docks into a druggable pocket of Ref-1 protein. In vitro studies revealed that resveratrol inhibited, in a dose-dependent manner, Ref-1-activated activator protein-1 DNA-binding activities as well as Ref-1 endonuclease activities and rendered melanoma cells more sensitive to dacarbazine treatment.


Subject(s)
DNA-(Apurinic or Apyrimidinic Site) Lyase/metabolism , Enzyme Inhibitors/pharmacology , Melanoma/enzymology , Stilbenes/pharmacology , DNA-(Apurinic or Apyrimidinic Site) Lyase/antagonists & inhibitors , DNA-(Apurinic or Apyrimidinic Site) Lyase/pharmacology , Electrophoretic Mobility Shift Assay , Fluorescent Antibody Technique , Humans , Melanocytes/drug effects , Recombinant Proteins/pharmacology , Resveratrol
12.
Acta Crystallogr D Biol Crystallogr ; 59(Pt 12): 2088-93, 2003 Dec.
Article in English | MEDLINE | ID: mdl-14646066

ABSTRACT

The first polygalacturonase from a plant, tomato fruit PG2, has been crystallized and data have been collected to a resolution of 1.87 A. The autoindexing program strongly favors one of the primitive orthorhombic cells. A plausible molecular-replacement solution for two molecules in the asymmetric unit has been found for data assigned to space group P2(1)2(1)2(1). Although the numerical criteria and the electron-density maps are reasonable for this solution, manually adjusted models do not refine to an R factor below 0.48. Visual inspection of hkl Bragg planes does not reveal a breakdown in mm symmetry. Nevertheless, the correct space group has been determined to be P2(1), with similar unit-cell parameters, a beta angle of 90.04 degrees and four molecules in the asymmetric unit. The R(sym) of 0.053 for data processed in P2(1)2(1)2(1) is very similar to the R(sym) of 0.047 for the same data processed in P2(1). Comparisons of the intermediate results using the P2(1)2(1)2(1) and P2(1) data sets are provided and the subtle indications of an initial erroneous space-group assignment are discussed.


Subject(s)
Polygalacturonase/chemistry , Solanum lycopersicum/enzymology , Crystallization , Crystallography, X-Ray , Fruit/enzymology , Models, Molecular , Protein Conformation
13.
Chem Biol ; 10(2): 161-8, 2003 Feb.
Article in English | MEDLINE | ID: mdl-12618188

ABSTRACT

The highly abundant GTP binding protein elongation factor Tu (EF-Tu) fulfills multiple roles in bacterial protein biosynthesis. Phage-displayed peptides with high affinity for EF-Tu were selected from a library of approximately 4.7 x 10(11) different peptides. The lack of sequence homology among the identified EF-Tu ligands demonstrates promiscuous peptide binding by EF-Tu. Homolog shotgun scanning of an EF-Tu ligand was used to dissect peptide molecular recognition by EF-Tu. All homolog shotgun scanning selectants bound to EF-Tu with higher affinity than the starting ligand. Thus, homolog shotgun scanning can simultaneously optimize binding affinity and rapidly provide detailed structure activity relationships for multiple side chains of a polypeptide ligand. The reported peptide ligands do not compete for binding to EF-Tu with various antibiotic EF-Tu inhibitors, and could identify an EF-Tu peptide binding site distinct from the antibiotic inhibitory sites.


Subject(s)
Peptide Elongation Factor Tu/antagonists & inhibitors , Peptide Library , Peptides/metabolism , Peptides/pharmacology , Amino Acid Sequence , Binding Sites , Cloning, Molecular , Enzyme-Linked Immunosorbent Assay , Escherichia coli/metabolism , Guanosine Diphosphate/metabolism , Molecular Sequence Data , Oligonucleotides/chemistry , Peptide Elongation Factor Tu/metabolism , Peptides/chemical synthesis , Protein Conformation , Reverse Transcriptase Polymerase Chain Reaction
14.
J Biol Chem ; 278(14): 12271-7, 2003 Apr 04.
Article in English | MEDLINE | ID: mdl-12540845

ABSTRACT

Ca(2+) is essential for in vitro activity of Erwinia chrysanthemi pectate lyase C (PelC). Crystallographic analyses of 11 PelC-Ca(2+) complexes, formed at pH 4.5, 9.5, and 11.2 under varying Ca(2+) concentrations, have been solved and refined at a resolution of 2.2 A. The Ca(2+) site represents a new motif for Ca(2+), consisting primarily of beta-turns and beta-strands. The principal differences between PelC and the PelC-Ca(2+) structures at all pH values are the side-chain conformations of Asp-129 and Glu-166 as well as the occupancies of four water molecules. According to calculations of pK(a) values, the presence of Ca(2+) and associated structural changes lower the pK(a) of Arg-218, the amino acid responsible for proton abstraction during catalysis. The Ca(2+) affinity for PelC is weak, as the K(d) was estimated to be 0.132 (+/-0.004) mm at pH 9.5, 1.09 (+/-0.29) mm at pH 11.2, and 5.84 (+/-0.41) mm at pH 4.5 from x-ray diffraction studies and 0.133 (+/-0.045) mm at pH 9.5 from intrinsic tryptophan fluorescence measurements. Given the pH dependence of Ca(2+) affinity, PelC activity at pH 4.5 has been reexamined. At saturating Ca(2+) concentrations, PelC activity increases 10-fold at pH 4.5 but is less than 1% of maximal activity at pH 9.5. Taken together, the studies suggest that the primary Ca(2+) ion in PelC has multiple functions.


Subject(s)
Calcium/metabolism , Dickeya chrysanthemi/metabolism , Isoenzymes/chemistry , Isoenzymes/metabolism , Polysaccharide-Lyases/chemistry , Polysaccharide-Lyases/metabolism , Binding Sites , Crystallography, X-Ray , Hydrogen-Ion Concentration , Protein Structure, Secondary , Protein Structure, Tertiary
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