Redox centers of 4-hydroxybenzoyl-CoA reductase, a member of the xanthine oxidase family of molybdenum-containing enzymes

4-Hydroxybenzoyl-CoA reductase (4-HBCR) is a key enzyme in the anaerobic metabolism of phenolic compounds. It catalyzes the reductive removal of the hydroxyl group from the aromatic ring yielding benzoyl-CoA and water. The subunit architecture, amino acid sequence, and the cofactor/metal content indicate that it belongs to the xanthine oxidase (XO) family of molybdenum cofactor-containing enzymes. 4-HBCR is an unusual XO family member as it catalyzes the irreversible reduction of a CoA-thioester substrate. A radical mechanism has been proposed for the enzymatic removal of phenolic hydroxyl groups. In this work we studied the spectroscopic and electrochemical properties of 4-HBCR by EPR and M?ssbauer spectroscopy and identified the pterin cofactor as molybdopterin mononucleotide. In addition to two different [2Fe-2S] clusters, one FAD and one molybdenum species per monomer, we also identified a [4Fe-4S] cluster/monomer, which is unique among members of the XO family. The reduced [4Fe-4S] cluster interacted magnetically with the Mo(V) species, suggesting that the centers are in close proximity, (<15 A apart). Additionally, reduction of the [4Fe-4S] cluster resulted in a loss of the EPR signals of the [2Fe-2S] clusters probably because of magnetic interactions between the Fe-S clusters as evidenced in power saturation studies. The Mo(V) EPR signals of 4-HBCR were typical for XO family members. Under steady-state conditions of substrate reduction, in the presence of excess dithionite, the [4Fe-4S] clusters were in the fully oxidized state while the [2Fe-2S] clusters remained reduced. The redox potentials of the redox cofactors were determined to be: [2Fe-2S](+1/+2) I, -205 mV; [2Fe-2S] (+1/+2) II, -255 mV; FAD/FADH( small middle dot)/FADH, -250 mV/-470 mV; [4Fe-4S](+1/+2), -465 mV and Mo(VI)/(V)/(VI), -380 mV/-500 mV. A catalytic cycle is proposed that takes into account the common properties of molybdenum cofactor enzymes and the special one-electron chemistry of dehydroxylation of phenolic compounds.     

Biotransformation of squamulosone by Curvularia lunata ATCC 12017

Squamulosone (aromadendr-1(10)-en-9-one), isolated in large quantity from the plant Hyptis verticillata Jacq. (Labiatae), was incubated with the fungus Curvularia lunata ATCC 12017 in two different growth media. Six metabolites were isolated from each medium. with five of the products being common to both fermentations. All seven metabolites are novel. The insecticidal activity of these aromadendranes was evaluated against the sweet potato weevil Cylas formicarius elegantus.     

15-LOX-1 inhibits p21 (Cip/WAF 1) expression by enhancing MEK-ERK 1/2 signaling in colon carcinoma cells

Currently, some controversy exists regarding the precise role of 15-lipoxygenase-1 (15-LOX-1) in colorectal carcinogenesis and other aspects of cancer biology. The aim of this study was to evaluate the effect of 15-LOX-1 on p21 (Cip/WAF 1) expression and growth regulation in human colon carcinoma cells. The effect of 13-S-hydroxyoctadecadienoic acid (HODE), a product of 15-LOX-1, on p21 (Cip/WAF 1) expression was evaluated in Caco-2 cells treated with sodium butyrate (NaBT) and/or nordihydroguaiarectic acid (NDGA), a LOX inhibitor. The effect of transfecting HCT-116 cells with 15-LOX-1 was also examined. NaBT-induced p21 (Cip/WAF 1) expression was enhanced by treatment with NDGA and 13-S-HODE reversed NaBT-induced p21 (Cip/WAF 1) expression in Caco-2 cells. Overexpression of 15-LOX-1 induced extracellular signal-related kinase (ERK) 1/2 phosphorylation, decreased p21 (Cip/WAF 1) expression, and increased HCT-116 cell growth. Treatment with NDGA decreased ERK 1/2 phosphorylation, and increased p21 (Cip/WAF 1) expression in 15-LOX-1 overexpressing HCT-116 cells. Our experimental results support the hypothesis that 15-LOX-1 may have "pro-neoplastic" effects during the development of colorectal cancer.     

Association between monocyte Fcgamma subclass expression and acute coronary syndrome

BACKGROUND: Atherosclerosis lesions contain abundant immunoglobulins complexed with oxidized LDL (OxLDL) that are endocytosed by macrophages to form foam cells. While recent evidence supports a role for the macrophage scavenger receptor pathway in 75-90% of OxLDL uptake, in vitro evidence suggests another potential uptake pathway could involve autoantibody binding to IgG subclass-specific Fc receptors. OBJECTIVE AND METHODS: To address this mechanism from an in vivo standpoint, the objective of this study was to utilize flow cytometry to prospectively determine monocyte Fcgamma (FcR) I, II, and III receptor expression levels in patients with acute coronary syndrome (ACS, n = 48), diabetes mellitus (DM, n = 59), or neither (C, n = 88). RESULTS: Increased FcR I expression was found in the ACS versus DM groups [geometric mean, (95% CI) = 2.26 (2.07, 2.47) versus 1.83 (1.69, 1.98) (p < 0.001)] and versus C [1.90 (1.78, 2.03) (p = 0.005)]. Similar relationships were found with both the FcR II receptor [ACS mean = 4.57 (4.02, 5.19) versus DM 3.61 (3.22, 4.05) (p = 0.021) and versus C 3.86 (3.51, 4.24) (p = 0.09)] and FcR III receptor [ACS mean = 1.55 (1.44, 1.68) versus DM 1.36 (1.27, 1.46) (p = 0.038) and versus C 1.37 (1.30, 1.45) (p = 0.032)]. There was no difference between DM and C groups in FcR I, II or III expression. CONCLUSIONS: This in vivo data supports a possible second OxLDL-autoantibody macrophage uptake mechanism through an Fc receptor-mediated pathway and a potential relationship between atherosclerotic plaque macrophage FcR levels and ACS.     

Automatic annotation of protein motif function with Gene Ontology terms

Background  

Conserved protein sequence motifs are short stretches of amino acid sequence patterns that potentially encode the function of proteins. Several sequence pattern searching algorithms and programs exist foridentifying candidate protein motifs at the whole genome level. However, amuch needed and importanttask is to determine the functions of the newly identified protein motifs. The Gene Ontology (GO) project is an endeavor to annotate the function of genes or protein sequences with terms from a dynamic, controlled vocabulary and these annotations serve well as a knowledge base.     

Developmental stress, social rank and song complexity in the European starling (Sturnus vulgaris)

Bird song is a sexually selected trait and females have been shown to prefer males that sing more complex songs. However, for repertoire size to be an honest signal of male quality it must be associated with some form of cost. This experiment investigates the effects of food restriction and social status during development on song complexity in the European starling (Sturnus vulgaris). Birds that experienced an unpredictable food supply early in life produced a significantly smaller repertoire of song phrases than those with a constant food supply. Social status during development was also significantly correlated with repertoire size, with dominant birds producing more phrase types. This study therefore provides novel evidence that social as well as nutritional history may be important in shaping the song signal in this species.