RRM proteins interacting with the cap region of topoisomerase I

RNA recognition motif (RRM) domains bind both nucleic acids and proteins. Several proteins that contain two closely spaced RRM domains were previously found in protein complexes formed by the cap region of human topoisomerase I, a nuclear enzyme responsible for DNA relaxation or phosphorylation of SR splicing proteins. To obtain molecular insight into specific interactions between the RRM proteins and the cap region of topo I we examined their binary interactions using the yeast two-hybrid system. The interactions were established for hnRNP A1, p54(nrb) and SF2/ASF, but not for hnRNP L or HuR. To identify the amino acid pattern responsible for binding, experimental mutagenesis was employed and computational modelling of these processes was carried out. These studies revealed that two RRM domains and six residues of the consensus sequence are required for the binding to the cap region. On the basis of the above data, a structural model for the hnRNP A1-topoisomerase I complex was proposed. The main component of the hnRNP A1 binding site is a hydrophobic pocket on the beta-surface of the first RRM domain, similar to that described for Y14 protein interacting with Mago. We demonstrated that the interaction between RRM domains and the cap region was important for the kinase reaction catalyzed by topoisomerase I. Together with the previously described inhibitory effect of RRM domains of SF2/ASF on DNA cleavage, the above suggests that the binding of RRM proteins could regulate the activity of topoisomerase I.     

Convergent Evolution of Human and Bovine Haptoglobin: Partial Duplication of the Genes

Haptoglobin (Hp) is a hemoglobin-binding plasma protein consisting of two types of chains, called α and β, which originate from a common polypeptide. In humans, but not in other mammals, Hp has been shown to occur in two allelic forms, Hp1 and Hp2, which differ in the length of the α-chain. The longer α-chain (in Hp2) seems to have arisen by an internal duplication of a gene segment coding for almost the entire α-chain of Hp1. In this article we show that Hp of cow (Bos taurus) contains an α-chain, the structure of which is similar to that of the human Hp2 α-chain. Furthermore, comparison of the structure of bovine Hp and human Hp2 suggests that the bovine gene arose by a duplication of the gene segment homologous to that duplicated in human Hp2. However, a phylogenetic analysis indicates that the two genes were formed independently. The evolutionary pressure that has led to the fixation of the Hps with a longer α-chain is not known. Reviewing Editor: Dr. Manyuan Long     

Visual rhodopsin sees the light: structure and mechanism of G protein signaling

The availability of crystal structures for the dark, inactive, and several light-activated photointermediate states of vertebrate visual rhodopsin has provided important mechanistic and energetic insights into the transformations underlying agonist-dependent activation of this and other G protein-coupled receptors (GPCRs). The high natural abundance of rhodopsin in the vertebrate retina, together with its specific localization to the disk membranes of the rod cell, has also enabled direct imaging of rhodopsin in its native environment. These advances have provided compelling evidence that rhodopsin, like many other GPCRs, forms highly organized oligomeric structures that, in all likelihood, are important for receptor biosynthesis, optimal activation, and signaling.     

Serum activity of dipeptidyl peptidase IV (DPPIV; EC 3.4.14.5) in breast-fed infants with symptoms of allergy

Beta-casomorphins, opioid peptides present in mother's milk, are a good substrate for DPPIV (EC 3.4.14.5) which is a major factor limiting the half-life of biologically active peptides. Serum DPPIV activity of two groups of infants (healthy and atopic dermatitis) and contents of beta-casomorphin-5 and -7 in their mothers' milk were determined in the study. We have found correlation between those two parameters in the group of children with atopic dermatitis syndromes, while no such a correlation was found in the control group.     

Changes of beta-casomorphin content in human milk during lactation

Milk is the best, complete food important for the development and nourishment of a neonate. Except for nutrients, milk contains biologically active opioid peptides derived from beta-casein, named beta-casomorphins (BCMs), which can exert effects in the gastrointestinal tract as well as in the whole body of neonates. The content of beta-casomorphins in human milk during maturation phases has not been studied so far. The aim of this study was to determine the content of beta-casomorphin-5 and -7 in human milk in different phases of lactation. A significantly higher concentration of both beta-casomorphins was found in colostrum than in mature milk. The concentration of beta-casomorphin in milk collected in the second month of lactation was similar to the level obtained in the fourth month of lactation. The content of beta-casomorphins in human milk was observed with the period of lactation. The level of opioid peptides may depend on the function of these peptides in neonate's body and may be associated with the maturation process.     

Thrombin activatable fibrinolysis inhibitor (TAFI) in cord blood

Thrombin activatable fibrinolysis inhibitor (TAFI) is a plasma zymogene (procarboxypeptidase B) which can decrease fibrinolysis and thus act as a haemostatic factor. TAFI is now extensively studied in many complications as well as in physiological and complicated pregnancy. The question we posed in the present study was whether TAFI antigen is present in cord blood plasma. The study group consisted of 38 parturient women, 26 primiparous and 12 multiparous with normal course of pregnancy and delivery. The cord blood was sampled from the cord vein, and the mother's blood from the antecubital vein. 3.2% sodium citrate was used as an anticoagulant. TAFIa/ai antigen was measured by ELISA method. TAFIa/ai antigen was identified in all samples of cord blood plasma. Its level was 91.50 ng/ml (range: 71.76 - 160.77 ng/ml) vs. 55.46 ng/ml (range: 39.77 - 68.54 ng/ml ) in the mother's blood, which means that the level of TAFIa/ai antigen was significantly higher in fetal blood than in maternal blood (p<0.00001). TAFIa/ai antigen is an integral component of cord blood plasma. The concentration of TAFIa/ai antigen is about two times higher in fetal blood than in maternal blood.     

Mycothiol import by Mycobacterium smegmatis and function as a resource for metabolic precursors and energy production

Mycothiol ([MSH] AcCys-GlcN-Ins, where Ac is acetyl) is the major thiol produced by Mycobacterium smegmatis and other actinomycetes. Mutants deficient in MshA (strain 49) or MshC (transposon mutant Tn1) of MSH biosynthesis produce no MSH. However, when stationary phase cultures of these mutants were incubated in medium containing MSH, they actively transported it to generate cellular levels of MSH comparable to or greater than the normal content of the wild-type strain. When these MSH-loaded mutants were transferred to MSH-free preconditioned medium, the cellular MSH was catabolized to generate GlcN-Ins and AcCys. The latter was rapidly converted to Cys by a high deacetylase activity assayed in extracts. The Cys could be converted to pyruvate by a cysteine desulfhydrase or used to regenerate MSH in cells with active MshC. Using MSH labeled with [U-(14)C]cysteine or with [6-(3)H]GlcN, it was shown that these residues are catabolized to generate radiolabeled products that are ultimately lost from the cell, indicating extensive catabolism via the glycolytic and Krebs cycle pathways. These findings, coupled with the fact the myo-inositol can serve as a sole carbon source for growth of M. smegmatis, indicate that MSH functions not only as a protective cofactor but also as a reservoir of readily available biosynthetic precursors and energy-generating metabolites potentially important under stress conditions. The half-life of MSH was determined in stationary phase cells to be approximately 50 h in strains with active MshC and 16 +/- 3 h in the MshC-deficient mutant, suggesting that MSH biosynthesis may be a suitable target for drugs to treat dormant tuberculosis.     

Sleep apnea: epidemiology, pathophysiology, and relation to cardiovascular risk

Several studies have shown the occurrence of an independent association between obstructive sleep apnea syndrome (OSAS) and cardiovascular disease, including arterial hypertension, ischemic heart disease, and stroke. The pathogenesis of the cardiovascular complications of OSAS is still poorly understood, however. Several mechanisms are likely to be involved, including sympathetic overactivity, selective activation of inflammatory molecular pathways, endothelial dysfunction, abnormality in the process of coagulation, and metabolic dysregulation. The latter may involve insulin resistance and disorders of lipid metabolism. The aim of this review, which reports the data presented at a workshop jointly endorsed by the European Society of Hypertension and by the European Union COST action on OSAS (COST B26), is to critically summarize the evidence available to support an independent association between OSAS and cardiovascular disease.