Kinetics of chemical modification of arginine and lysine residues in calf thymus histone H1

The arginine and lysine residues of calf thymus histone H1 were modified with large molar excesses of 2,3-butanedione and O-methylisourea, respectively. Kinetic study of the modification reaction of the arginine residue revealed that the reaction is divided into the two pseudo-first-order processes. About a third (1 Arg) of the total arginine residues of the H1 molecule was rapidly modified without causing any detectable structural change of the molecule, and the slow modification of the remaining arginine residues (2 Arg) led to a loss of the folded structure of H1. In the case of lysine residue modification, 93% (56 Lys) of the total lysine residues of the H1 was modified with the same rate constant, while 7% (4 Lys) of lysine residue remained unmodified. When the reaction was performed in the presence of 6M guanidine-HCl, all of lysine residues were modified. It is concluded that the 2 arginine and 4 lysine residues resistant to modification are buried in interior regions of the H1 molecule and play an important role in the formation of the H1 globular structure, while the other 1 arginine and 56 lysine residues are exposed to solvent.     

A temperature-sensitive mutant of cultured mouse cells defective in chromosome condensation

A temperature-sensitive mutant, designated ts85, was isolated from a mouse mammary carcinoma cell line, FM3A. The ts85 cells grew at 33 °C (permissive temperature) with a doubling time of 18 h, which was almost the same as with wild-type cells, whereas the cell number scarcely increased at all at 39 °C (non-permissive temperature). When the ts85 cells were shifted from 33 to 39 °C, their DNA synthesis fell to below 1% of the initial value in 14 h. RNA or protein synthesis, however, was maintained at the initial levels for at least 14 h at 39 °C. Cytofluorometric analysis of asynchronous cultures and studies with synchronous cultures suggested that the bulk of the cells cultured at 39 °C for 12–18 h were arrested in late S and G2 phases. Electron microscopic observations revealed that chromatin was abnormally condensed into fragmented and compact forms, particularly around nucleoli, in about 80% of cells of an asynchronous culture incubated at 39 °C for 16 h. Cells in mitosis were not detected in such cultures and nuclear membrane and nucleoli were still intact. Such abnormal chromosome condensation was not observed in the ts85 cells at 33 °C or in wild-type cells at either temperature. Since these findings suggest that a ts gene product of ts85 cells is necessary for chromosome condensation, ts85 cells may represent a useful tool for establishing the mechanisms of chromosome condensation. The interrelationship between abnormal chromosome condensation and reduction in DNA synthesis of the ts85 cells is discussed.     

Adenosine and adenine nucleotides stimulation of skin (epidermal) adenylate cyclase

Adenosie, AMP, ADP and ATP activated adenylate cyclase in pig skin (epidermis) slices resulting in the accumulation of cyclic AMP. This effect was highly potentiated by the addition of the cyclic AMP-phophodiesterase inhibitor, papaverine. But another inhibitor, theophylline, strongly blocked the activation of adenylate cyclase by adenosine and adenine nucleotides. Theophylline apparently competed with adenosine for the cell suface receptor. Like theophylline, the addition of adenine alone caused no accumulation of cyclic AMP, but it significantly inhibited the stimulatory effect of adenosine. Guanosine, or guanine, cytidine, uridine, or thymidine nucleotides has no effect on the accumulation of cyclic AMP. Among other adenine nucleotides was tested, adenosine 5′-monophosphoramidate, but not adenosine 5′-monosulfate, significantly increased cyclic AMP especially with the addition of papaverine. Neither 2′- nor 3′-adenylic acid were effective. Our data indicate that pig epidermis has four specific and independent adenylate cyclase systems for adenosine (and adenine nucleotides), histamine, epinephrine and prostaglandin E.     

Oxygen concentration-dependent induction of a 140-kDa protein in magnetic bacterium Magnetospirillum magnetotacticum MS-1

Abstract The magnetic bacterium Magnetospirillum magnetotacticum prefers a microaerobic habitat and should be able to sense oxygen. Therefore, the bacterium was cultured under atmospheres containing 0–5% O₂ and analyzed for oxygen-dependent changes in the levels of its protein components by sodium dodecyl sulfate-polyccrylamide gel electrophoresis (SDS-PAGE). The analysis revealed a marked anaerobic induction of a 140-kDa protein, which was suppressed when M. magnetotacticum was switched from microaerobic (<1% O₂) to aerobic (>1% O₂) growth conditions. Although its function remains to be determined, the 140-kDa protein may serve as a useful tool to gain insight into the physiology of the organism.     

The L-Cysteine Desulfurase NFS1 Is Localized in the Cytosol where it Provides the Sulfur for Molybdenum Cofactor Biosynthesis in Humans

In humans, the L-cysteine desulfurase NFS1 plays a crucial role in the mitochondrial iron-sulfur cluster biosynthesis and in the thiomodification of mitochondrial and cytosolic tRNAs. We have previously demonstrated that purified NFS1 is able to transfer sulfur to the C-terminal domain of MOCS3, a cytosolic protein involved in molybdenum cofactor biosynthesis and tRNA thiolation. However, no direct evidence existed so far for the interaction of NFS1 and MOCS3 in the cytosol of human cells. Here, we present direct data to show the interaction of NFS1 and MOCS3 in the cytosol of human cells using Förster resonance energy transfer and a split-EGFP system. The colocalization of NFS1 and MOCS3 in the cytosol was confirmed by immunodetection of fractionated cells and localization studies using confocal fluorescence microscopy. Purified NFS1 was used to reconstitute the lacking molybdoenzyme activity of the Neurospora crassa nit-1 mutant, giving additional evidence that NFS1 is the sulfur donor for Moco biosynthesis in eukaryotes in general.     

Emergence of artemisinin-resistant Plasmodium falciparum with kelch13 C580Y mutations on the island of New Guinea

The rapid and aggressive spread of artemisinin-resistant Plasmodium falciparum carrying the C580Y mutation in the kelch13 gene is a growing threat to malaria elimination in Southeast Asia, but there is no evidence of their spread to other regions. We conducted cross-sectional surveys in 2016 and 2017 at two clinics in Wewak, Papua New Guinea (PNG) where we identified three infections caused by C580Y mutants among 239 genotyped clinical samples. One of these mutants exhibited the highest survival rate (6.8%) among all parasites surveyed in ring-stage survival assays (RSA) for artemisinin. Analyses of kelch13 flanking regions, and comparisons of deep sequencing data from 389 clinical samples from PNG, Indonesian Papua and Western Cambodia, suggested an independent origin of the Wewak C580Y mutation, showing that the mutants possess several distinctive genetic features. Identity by descent (IBD) showed that multiple portions of the mutants’ genomes share a common origin with parasites found in Indonesian Papua, comprising several mutations within genes previously associated with drug resistance, such as mdr1, ferredoxin, atg18 and pnp. These findings suggest that a P. falciparum lineage circulating on the island of New Guinea has gradually acquired a complex ensemble of variants, including kelch13 C580Y, which have affected the parasites’ drug sensitivity. This worrying development reinforces the need for increased surveillance of the evolving parasite populations on the island, to contain the spread of resistance.     

Heat shock response in olive (Olea europaea L.) twigs: Identification and analysis of a cDNA coding a class I small heat shock protein

Abstract

The objective of this study was to investigate at the molecular level the heat shock response in olive by identifying sequences coding for heat shock proteins (HSPs). Young twigs of Olea europaea trees (cv Cellina di Nardò) were subjected to different temperature treatments in order to induce the expression of heat shock genes. In order to identify genes induced by heat treatment, we used a PCR-based approach to amplify specific HS cDNAs. Search for low molecular weight HSP sequences was performed in public domain databases in order to design specific primers based upon multisequence alignments. By this approach, we isolated the first full length cDNA encoding a low-molecular weight HSP from O. europaea. This is a class I low molecular weight HSP of 18.3 kDa, which is highly expressed in young twigs subjected to heat stress.     

Pathway of Glycine Betaine Biosynthesis in Aspergillus fumigatus

The choline oxidase (CHOA) and betaine aldehyde dehydrogenase (BADH) genes identified in Aspergillus fumigatus are present as a cluster specific for fungal genomes. Biochemical and molecular analyses of this cluster showed that it has very specific biochemical and functional features that make it unique and different from its plant and bacterial homologs. A. fumigatus ChoAp catalyzed the oxidation of choline to glycine betaine with betaine aldehyde as an intermediate and reduced molecular oxygen to hydrogen peroxide using FAD as a cofactor. A. fumigatus Badhp oxidized betaine aldehyde to glycine betaine with reduction of NAD⁺ to NADH. Analysis of the AfchoAΔ::HPH and AfbadAΔ::HPH single mutants and the AfchoAΔAfbadAΔ::HPH double mutant showed that AfChoAp is essential for the use of choline as the sole nitrogen, carbon, or carbon and nitrogen source during the germination process. AfChoAp and AfBadAp were localized in the cytosol of germinating conidia and mycelia but were absent from resting conidia. Characterization of the mutant phenotypes showed that glycine betaine in A. fumigatus functions exclusively as a metabolic intermediate in the catabolism of choline and not as a stress protectant. This study in A. fumigatus is the first molecular, cellular, and biochemical characterization of the glycine betaine biosynthetic pathway in the fungal kingdom.