Polypeptides from maize seedlings with protein kinase functions

Low molecular weight protein kinase from maize seedlings was isolated. The molecular weight of the enzyme was below 10 000. The enzyme preferentially utilized ATP and casein as donor and acceptor of phosphorus, respectively. Casein kinase was a cyclic nucleotide-independent, heparin-sensitive enzyme. The low molecular weight casein kinase was resolved into basic, neutral and slightly acidic peaks of activity by chromatofocussing.     

Regiospecificity of Human Cytochrome P450 1A1-Mediated Oxidations: The Role of Steric Effects

Abstract

Cytochrome P450 1A1 oxidizes a diverse range of substrates, including the procarcinogenic xenobiotic benzo[a]pyrene (B[a]P) and endogenous fatty acid precursors of prostaglandins, such as arachidonic acid (AA) and eicosapentaenoic acid (EA). We have investigated the extent to which enzyme-substrate interactions govern regio- and stereoselectivity of oxidation of these compounds by using docking and molecular dynamics (MD) simulations to examine the likelihood of substrate oxidation at various sites. Due to structural differences between the substrates analyzed, B[a]P and its diols (planar, rigid), and the fatty acids AA and EA (long, flexible), different docking strategies were required. B[a]P, B[a]P-7,8-diols, (+) 7S,85- and (-) 7R,8R-diols, were docked into the active site of a homology model of P450 1A1 using an automated routine. Affinity (Accelrys, San Diego, CA). AA and EA, on the other hand, required a series of restrained MD simulations to obtain a variety of productive binding modes. All complexes were evaluated by MD-based in silico site scoring to predict product profiles based on certain geometric criteria, such as angle and distance of a given substrate atom from the ferryl oxygen. For all substrates studied, the in vitro profiles were generally reflected by the in silico scores, which suggests that steric factors play a key role in determining regiospecificity in P450 1A1-mediated oxidations. We have also shown that molecular dynamics simulations may be very useful in determination of product profiles for structurally diverse substrates of P450 enzymes.     

Iron–sulfur biology invades tRNA modification: the case of U34 sulfuration

Sulfuration of uridine 34 in the anticodon of tRNAs is conserved in the three domains of life, guaranteeing fidelity of protein translation. In eubacteria, it is catalyzed by MnmA-type enzymes, which were previously concluded not to depend on an iron–sulfur [Fe–S] cluster. However, we report here spectroscopic and iron/sulfur analysis, as well as in vitro catalytic assays and site-directed mutagenesis studies unambiguously showing that MnmA from Escherichia coli can bind a [4Fe–4S] cluster, which is essential for sulfuration of U34-tRNA. We propose that the cluster serves to bind and activate hydrosulfide for nucleophilic attack on the adenylated nucleoside. Intriguingly, we found that E. coli cells retain s²U34 biosynthesis in the ΔiscUA ΔsufABCDSE strain, lacking functional ISC and SUF [Fe–S] cluster assembly machineries, thus suggesting an original and yet undescribed way of maturation of MnmA. Moreover, we report genetic analysis showing the importance of MnmA for sustaining oxidative stress.     

NO-dependent phototoxicity of Roussin's black salt against cancer cells.

A metal-nitrosyl complex, Roussin's black salt (RBS), releases nitric oxide after illumination. Approximately 3.7 NO molecules were released from one RBS molecule. Both short- and long-term effects of photogenerated NO on the two neoplastic cell lines: human (SK-MEL188) and mouse (S91) have been investigated. Exogenous NO from RBS was toxic to cells in a dose-dependent manner. Apoptotic damage predominates in the response to the injury, as shown by TUNEL assay. NO and its short-lived metabolites, but not other RBS photoproducts, are responsible for cellular death. RBS in dark was toxic to cells at concentrations above 1 microM. This relatively high cytotoxicity of RBS in the dark prevents its application as a systemic anticancer agent in vivo, unless it is applied locally.     

Structure of Syncytia Induced by Heterodera avenae Woll. in Roots of Susceptible and Resistant Wheat (Triticum aestivum L.)

The structure of syncytia induced by Heterodera avenae in roots of susceptible Triticum aestivum cv. ‘Capa’ and resistant wheat AUS 10894 was investigated. In susceptible plants the first syncytia were observed 4 days after placing the seedlings into a substrate containing nematode cysts. They were located on different root levels. In resistant plants syncytia were first found after 14 days, exclusively in the root maturity zone. In both wheats syncytia consisted mostly of stelar parenchymatic cells. The syncytia induced in roots of Triticum aestivum AUS 10894 were characterized by less immediate contact with the host tracheary elements than the syncytia induced in roots of susceptible Triticum aestivum cv. ‘Capa’. In both wheats a stimulation of pericycle cell divisions, giving rise to lateral roots, was found in parts where the syncytia developed.     

Variation in sociosexuality across natural menstrual cycles: Associations with ovarian hormones and cycle phase

The psychological construct of sociosexuality—one's sexual openness or propensity to engage in uncommitted sexual relationships—has been broadly examined within numerous cultures and mating contexts. Although there is some evidence suggesting that components of sociosexuality, namely behavior, desire and attitude, change within-person, relatively little research has investigated potential sources of such variation. The aim of our study was to explore if the individual components of sociosexuality change across the menstrual cycle, either as a function of cycle phase or ovarian hormones. One hundred and two naturally cycling women, both single and in a committed relationships, completed questions from the the SOI-R (Sociosexuality Revised) questionnaire three times during a menstrual cycle, scheduled to coincide with their early follicular, peri-ovulatory, and luteal phases. Women provided saliva samples and performed luteinizing hormone tests to distinguish between ovulatory and anovulatory cycles. Women reported slightly more openness to uncommitted sexual relationships during the peri-ovulatory session, but significant differences were restricted only to women who exhibited the luteinizing hormone surge. Ovarian hormone concentrations within cycles significantly predicted SOI Attitude and Desire scores, with estradiol positively related, and progesterone negatively related to openness to uncommitted sexuality. These effects were generally modest in size. The results of this study suggest that sociosexuality can vary within short periods of time, such as a single menstrual cycle.     

Differences between the conformations of nitrotyrosyl-248 carboxypeptidase A in the crystalline state and in solution

In solution, nitrocarboxypeptidase A, modified at tyrosyl-248, exhibits a nitrotyrosyl pK apparent of 6.3. In the crystalline state, the pK apparent is about 8.2. This change in ionization is consistent with the hypothesis that crystallization of the enzyme causes a displacement of tyrosine-248 away from the active site zinc ion.