Fahr Syndrome - an Important Piece of a Puzzle in the Differential Diagnosis of Many Diseases

Fahr syndrome is a rare neurodegenerative disorder characterized by symmetrical, bilateral calcifications in the basal ganglia, nucleus gyrus and cerebral cortex. The continuous advancement as well as widespread use of brain imaging have contributed to the increasing detection rates of such changes. Nevertheless, their etiology is understood only partially and the methods of causative treatment are limited. Due to various symptoms, Fahr syndrome may resemble diseases from the field of neurology, psychiatry, cardiology and even urology. This article provides an up-to-date review of the literature concerning Fahr syndrome in terms of clinical practice.

The Hippeastrum hybridum PepR1 gene (HpPepR1) encodes a functional guanylyl cyclase and is involved in early response to fungal infection

It is generally known that cyclic GMP widespread in prokaryotic and eukaryotic cells, is involved in essential cellular processes and stress signal transduction. However, in contrast to animals the knowledge about plant guanylyl cyclases (GCs) which catalyze the formation of cGMP from GTP is still quite obscure. Recent studies of plant GCs are focused on identification and functional analysis of a new family of membrane proteins called "moonlighting kinases with GC activity" with guanylyl cyclase catalytic center encapsulated within intracellular kinase domain. Here we report identification and characterization of plasma membrane receptor of peptide signaling molecules - HpPepR1 in Hippeastrum hybridum. Both bioinformatic analysis of amimo acid sequence and in vitro studies revealed that the protein can act as guanylyl cyclase. The predicted amino acid sequence contains highly conserved 14 aa-long search motif in the catalytic center of GCs from lower and higher eukaryotes. Here, we provide experimental evidence to show that the intracellular domain of HpPepR1 can generate cGMP in vitro. Moreover, it was shown that the accumulation of HpPepR1 transcript was sharply increased after Peyronellaea curtisii (=Phoma narcissi) fungal infection, whereas mechanical wounding has no influence on expression profile of studied gene. These results may indicate the participation of cGMP-dependent pathway in rapid, alarm plant reactions induced by pathogen infection.

Transcriptional response of a novel HpCDPK1 kinase gene from Hippeastrum x hybr. to wounding and fungal infection

Calcium dependent protein kinases (CDPK) are well established plant sensor and effectors for calcium ions and participate in regulation of multiple abiotic and biotic stress responses in plant cells. Here we present the identification and characterization of a new CDPK kinase gene from bulbous plant Hippeastrum x hybr. and examine the role of this kinase in stress responses leading to phytoalexin (PA) production in plant tissues. In the previous research, it was shown that Hippeastrum bulbs mechanically wounded or infected with Peyronellaea curtisii (=Phoma narcissi) are inducted to an antifungal red substance synthesis. In this research, we demonstrated Ca²⁺ dependence of the phytoalexin production by wounded bulbs. Furthermore, the isolated HpCDPK1 cDNA for ORF was found to be 1596bp long and encoded 531 amino acid protein with CDPK kinase activity, as was shown by recombinant GST-HpCDPK1 enzyme production and analysis. HpCDPK1 transcript was present in all vegetative and chosen generative organs of Hippeastrum plant. The dynamics of the observed HpCDPK1 mRNA changes in bulbs depended on stressor type. The mechanical injury caused one wave of transcript increase while more complex transcript changes were observed within 48h after Peyronellaea inoculation. In plant bulbs already accumulating red phytoalexin, increases in HpCDPK1 mRNA level were observed at certain intervals within 48h whereas, in the case of fungal infection, only one big increment in the transcript amount at the 10th minute after inoculation was detected. The observed transcriptional response of HpCDPK1 gene to wounding and pathogen infection stress suggests a positive correlation with phytoalexin synthesis and maintenance in bulb tissues and puts more light on CDPK kinase role in the plant stress response regulation. This also bears some potential for understanding the mechanism of a phytoalexin formation.

PCSK9 inhibitors - from discovery of a single mutation to a groundbreaking therapy of lipid disorders in one decade

Hypercholesterolemia is one of the main risk factors for coronary heart disease and significantly contributes to the high mortality associated with cardiovascular diseases. Statin therapy represents the gold standard in the reduction of low-density lipoprotein cholesterol concentration. Nevertheless, many patients still cannot achieve the recommended target levels, due to either inadequate effectiveness or intolerance of these drugs. Monoclonal antibodies that inhibit proprotein convertase subtilisin/kexin type 9 (PCSK9) have emerged as a promising option in lipid-lowering treatment. After confirmation of their efficacy and safety in clinical trials, evolocumab and alirocumab received approval from the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) for introduction into clinical practice. In this review, we present a history of the development and mechanisms of action, as well as the results of the most important studies concerning PCSK9 inhibitors.

[New strategies for assessing the risk of sudden cardiac death in hypertrophic cardiomyopathy]

Hypertrophic cardiomyopathy (HCM) is characterized by a primarily increased ventricular wall thickness, usually caused by the mutations in genes encoding sarcomere proteins. Thanks to the growing awareness in the medical community as well as advances in diagnostic techniques HCM can be diagnosed at earlier stages than ever before. However, in some cases the first symptom of this disease is a sudden cardiac death (SCD) and diagnosis remains unknown until post-mortem examination. Implantation of a cardioverterdefibrillator (ICD) provides the most effective method of SCD prevention. Nevertheless, due to a number of risks associated with surgery as well as the possession of such devices, predictive factors of serious ventricular arrhythmia in individual patients have been sought for many years. The aim of this review is to present the current strategies of risk assessment and prevention of SCD in patients with HCM.

Identification of a Hippeastrum hybridum guanylyl cyclase responsive to wounding and pathogen infection

Guanosine 3',5'-cyclic monophosphate (cGMP) is a critical component of many (patho)physiological processes in plants whilst guanylyl cyclases (GCs) which catalyse the formation of cGMP from GTP have remained somewhat elusive. Consequently, the two major aims are the discovery of novel guanylyl cyclases and the identification of GC/cGMP mediated processes. To identify a novel GC from Hippeastrum hybridum plant and facilitate the preparation of guanylyl cyclase in an amount sufficient for further crystallographic studies, we have constructed an overproduction system for this enzyme. This gene encodes a protein of 256 amino acids, with a calculated molecular mass of 28kD. The predicted amino acid sequence contains all the typical features and shows a high identity to other plant GCs. The GST-HpGC1 was catalytically active in Escherichia coli cells and the purified, recombinant HpGC1 was able to convert GTP to cGMP in the presence of divalent cations. The used overexpression system yields a guanylyl cyclase as 6% of the bacterial cytosolic protein. Besides the identification of HpGC1 as a guanylyl cyclase, the study has shown that the level of HpCG1 mRNA changed during stress conditions. Both mechanical damage and a Peyronellaea curtisii (=Phoma narcissi) fungi infection led to an initial decrease in the HpGC1 transcript level, followed by a substantial increase during the remainder of the 48-h test cycle. Moreover, significant changes in cyclic GMP level were observed, taking the form of oscillations. In conclusion, our data unequivocally identified the product of the HpGC1 gene as a guanylyl cyclase and demonstrates that such an overproduction system can be successfully used in enzyme synthesis. Furthermore, they indicate a link between the causing stimulus (wounding, infection) and guanylyl cyclase expression and the increase in cGMP amplitude. Therefore, it is concluded that appearance of cyclic GMP as a mediator in defense and wound-healing mechanisms provides a clue to the regulation of these processes.

Genomic structure and promoter characterization of the CDPK kinase gene expressed during seed formation in Pharbitis nil

CDPK kinases are a unique class of calcium sensor/responders that regulate many growth and developmental processes as well as stress responses of plants. PnCDPK1 kinase from Pharbitis nil is regulated by light and contributes to seed germination, seedling growth and flower formation. Following an earlier work in which we identified the PnCDPK1 coding sequence and a 330bp long 3'UTR (untranslated region), we present for the first time the genomic organization of PnCDPK1, including intron analysis and the gene copy number designation. We completed the research by identifying the 5'-flanking region of PnCDPK1 and analyzed it in silico, which led to the discovery of several cis-regulatory elements involved in light regulation, embryogenesis and seed development. The functional analysis of P. nil CDPK showed characterization of the PnCDPK1 transcript and PnCDPK protein level during seed formation and fruit maturation. The greatest amount of PnCDPK1 mRNA was present in the last stages of seed maturation. Moreover, two PnCDPK proteins of different molecular masses were discovered during fruit development, showing various protein accumulation and activity profile. The 56kDa protein dominated in the early stages of fruit development, whereas the smaller protein (52kDa) was prominent in the latter stages.

Cutaneous adverse reactions of amiodarone

Dermatological complications of amiodarone are commonly encountered problems in therapy. The incidence in the population of patients with prolonged use of amiodarone reaches nearly 75% according to various sources. Nevertheless, they are often misdiagnosed or overlooked. The aim of this review is to present the current state of knowledge about skin changes induced by amiodarone, including phototoxic and photoallergic reactions, as well as hyperpigmentation. In most cases, the adverse effects are reversible and disappear after discontinuation of the drug. Although the dermatological complications usually do not influence the outcome of the therapy and rarely cause discontinuation of treatment, they have a great impact on patient quality of life.

Transfusion-related acute lung injury: a dangerous and underdiagnosed noncardiogenic pulmonary edema

Transfusion-related acute lung injury (TRALI) is one of the leading causes of death associated with transfusion of blood and blood components. The understanding of the etiology and pathophysiology of this syndrome has much improved during the last decades, nevertheless numerous issues are still unresolved and symptomatic treatment remains the cornerstone of medical management. Consequently more attention is directed at primary as well as secondary prevention. The awareness of the problem within the medical society is still unsatisfactory which results in a high number of unrecognized cases or of inaccurate diagnoses one of which is cardiogenic pulmonary edema. The aim of this review is to make the TRALI syndrome more familiar to clinicians and to emphasize how significant proper medical management is both for the patients presenting TRALI symptoms as well as for future recipients of blood components.

Molecular cloning and characterization of a novel adenylyl cyclase gene, HpAC1, involved in stress signaling in Hippeastrum x hybridum

Adenylyl cyclases (ACs) are enzymes that generate cyclic AMP, which is involved in different physiological and developmental processes in a number of organisms. Here, we report the cloning and characterization of a new plant adenylyl cyclases (AC) gene, designated HpAC1, from Hippeastrum x hybridum. This gene encodes a protein of 206 amino acids with a calculated molecular mass of 23 kD and an isoelectric point of 5.07. The predicted amino acid sequence contains all the typical features of and shows high identity with putative plant ACs. The purified, recombinant HpAC1 is able to convert ATP to cAMP. The complementation test that was performed to analyze the ability of HpAC1 to compensate for the AC deficiency in the Escherichia coli SP850 strain revealed that HpAC1 functions as an adenylyl cyclase and produces cyclic AMP. Moreover, it was shown that the transcript level of HpAC1 and cyclic AMP concentration changed during certain stress conditions. Both mechanical damage and Phoma narcissi infection lead to two sharp increases in HpAC1 mRNA levels during a 72-h test cycle. Changes in intracellular cAMP level were also observed. These results may indicate the participation of a cAMP-dependent pathway both in rapid and systemic reactions induced after disruption of symplast and apoplast continuity.

The calcium-dependent protein kinase (PnCDPK1) is involved in Pharbitis nil flowering

Signaling pathways, and specifically the signaling pathway of calcium, have been widely implicated in the regulation of a variety of signals in plants. Calcium-dependent protein kinases (CDPKs) are essential sensor-transducers of calcium signaling pathways, the functional characterization of which is of great interest because they play important roles during growth and in response to a wide range of environmental and developmental stimuli. Here, we report the first evidence of transient and specific elevation of PnCDPK1 transcript level and enzyme activity following conversion of a leaf bud to a flower bud, as well as participation of PnCDPK1 in evocation and flower morphogenesis in Pharbitis nil. Fluorescence microscopy immunolocalization and biochemical analysis confirmed the presence of CDPK in shoot apexes. The protein level was low in leaves, vegetative apexes and increased significantly in apexes after a flowering long-induction night. In the vegetative apex, a very weak PnCDPK1 protein signal was accumulated prominently in the zone of the ground meristem and in external layers of tissues of the cortex. After the dark treatment, the signal in cells of the ground meristem was still present, but a significantly stronger signal appeared in epidermal cells, cortex tissue, and leaf primordium. At the onset of flower meristem development, the PnCDPK1 level diverged significantly. PnCDPK1 mRNA, protein level and enzyme activity were very low at the beginning of flower bud development and gradually increased in later stages, reaching the highest level in a fully open flower. Analysis of flower organs revealed that PnCDPK1 was accumulated mainly in petals and sepals rather than in pistils and stamens. Our results clearly indicate that PnCDPK1 is developmentally regulated and may be an important component in the signal transduction pathways for flower morphogenesis. Findings from this research are important for further dissecting mechanisms of flowering and functions of CDPKs in flowering plants.

[Role of inflammation in etiology of atrial fibrillation--is lone arrhythmia really alone]

We present the case study of recurrent AF episodes initially considered as a lone arrhythmia. Due to elevated C-reactive protein and fibrinogen serum levels with absence of other potential risk factors of arrhythmia and diseases underlying the genesis of inflammatory response we consider the plays a prominent role in etiology in perpetuation and maintenance of AF. Additional use of atorvastatin to a conventional therapy leads to significant reduction of C-reactive protein and fibrinogen and improves effect of long-term sinus rhythm maintenance.

Calreticulin expression and localization in plant cells during pollen-pistil interactions

In this report, the distributions of calreticulin (CRT) and its transcripts in Haemanthus pollen, pollen tubes, and somatic cells of the hollow pistil were studied. Immunoblot analysis of protein extracts from mature anthers, dry and germinated pollen, growing pollen tubes, and unpollinated/pollinated pistils revealed a strong expression of CRT. Both in vitro and in situ studies confirmed the presence of CRT mRNA and protein in pollen/pollen tubes and somatic cells of the pistil transmitting tract. The co-localization of these molecules in ER of these cells suggests that the rough ER is a site of CRT translation. In the pistil, accumulation of the protein in pollen tubes, transmitting tract epidermis (tte), and micropylar cells of the ovule (mc) was correlated with the increased level of exchangeable calcium. Therefore, CRT as a Ca(2+)-binding/buffering protein, may be involved in mechanism of regulation calcium homeostasis in these cells. The functional role of the protein in pollen-pistil interactions, apart from its postulated function in cellular Ca(2+) homeostasis, is discussed.

Effect of light on soluble guanylyl cyclase activity in Pharbitis nil seedlings

Cyclic GMP acts as a chemical switch in plant cells to modulate cellular reactions. However, its metabolism has not been extensively explored and is still poorly understood. Previous experiments suggest that an endogenous cGMP system could participate in the mechanism of phytochrome controlled photoperiodic flower induction in Pharbitis nil. In order to gain further information on the role of cGMP, we have begun to study the enzyme of cGMP synthesis. In this article, the presence of the enzyme with guanylyl cyclase (GC) activity in soluble protein fractions of P. nil is reported. A large portion of the enzymatic activity is present in the cotyledons, where enzyme activity amounted to 0.45 pmol cGMP/min/mg protein. The enzyme exhibited a K(m) 0.5mM for GTP. A plot of 1/v versus 1/[GTP] was linear and V(max) was 0.74 pmol cGMP/min/mg protein. It was shown that the anti-sGC antibody recognise a 40 kDa protein. Moreover, the NO-donor, sodium nitroprusside (SNP) and YC-1, as a NO-independent stimulator, enhanced enzyme activity. The NS 2028 (a potent GC inhibitor) treatments provoked a 3-fold reduction of the enzyme activity in comparison to the untreated fractions. Furthermore, the influence of light on GC activity was analysed. It was noted that cGMP level increased in cool white light, and darkness inhibited enzyme activity. Exposure to blue light acts to stimulate cGMP formation, whereas in red light a rapid decrease in GC activity was observed that returned to the high level when far-red light was applied after the red light treatment. The results presented in this work strongly argue that an enzyme with guanylyl cyclase activity is present in P. nil organs and its activity is controlled by light via the photoreceptors-dependent pathways.

Involvement of cyclic GMP in phytochrome-controlled flowering of Pharbitis nil

Light is one of the most important environmental factors influencing the induction of flowering in plants. Light is absorbed by specific photoreceptors--the phytochromes and cryptochromes system--which fulfil a sensory and a regulatory function in the process. The absorption of light by phytochromes initiates a cascade of related biochemical events in responsive cells, and subsequently changes plant growth and development. Induction of flowering is controlled by several paths. One is triggered by the guanosine-3':5'-cyclic monophosphate (cGMP) level. Thus, the aim of our study was to investigate the role of cGMP in phytochrome-controlled flowering. It is best to conduct such research on short-day plants because the photoperiodic reactions of only these plants are totally unequivocal. The most commonly used plant is the model short-day plant Pharbitis nil. The seedlings of P. nil were cultivated under special photoperiodic conditions: 72-h-long darkness, 24-h-long white light with low intensity and 24-h-long inductive night. Such light conditions cause a degradation of the light-labile phytochrome. Far red (FR) treatment before night causes inactivation of the remaining light-stable phytochrome. During the 24-h-long inductive darkness period, the total amount of cGMP in cotyledons underwent fluctuations, with maxima at the 4th, 8th and 14th hours. When plants were treated with FR before the long night, fluctuations were not observed. A red light pulse given after FR treatment could reverse the effect induced by FR, and the oscillation in the cGMP level was observed again. Because the intracellular level of cGMP is controlled by the opposite action of guanylyl cyclases (GCs) and phosphodiesterases (PDEs), we first tested whether accumulation of the nucleotide in P. nil tissue may be changed after treatment with a GC stimulator or PDE inhibitor. Accumulation of the nucleotide in P. nil cotyledons treated with a stimulator of cGMP synthesis (sodium nitroprusside) was markedly (approximately 80%) higher. It was highest in the presence of dipyridamole, whereas 3-isobutyl-1-methylxanthine did not significantly affect cGMP level. These results show that the analysed compounds were able to penetrate the cotyledons' tissue, and that they influenced enzyme activity and cGMP accumulation. FR light applied at the end of the 24-h-long white light period inhibited flowering. Exogenous cGMP added on cotyledons could reverse the effect of FR, especially when the compound was applied in the first half of the long night. Flowering was also promoted by exogenous application of guanylyl cyclase activator and phosphodiesterase inhibitors, and in particular dipyridamole. The results obtained suggest that an endogenous cGMP system could participate in the mechanism of a phytochrome-controlled flowering in P. nil.

Pharmacokinetics of florfenicol, thiamphenicol, and chloramphenicol in turkeys

The pharmacokinetics of florfenicol (FF), thiamphenicol (TP) and chloramphenicol (CP) after single intravenous (i.v.) or oral (p.o.) administration was studied in an independent cross-over study in broiler turkeys. All the fenicol antibiotics were administered at a dose of 30 mg/kg b.w. and their concentrations in plasma samples were assayed using the same validated high-performance liquid chromatography method. Pharmacokinetic parameters were calculated by a noncompartmental method. The kinetic profiles of the compounds were compared with the results of the structure-activity relationship. According to the proposed mathematical description, no differences in plasma clearance values for the studied antibiotics were observed. The mean residence time values of FF, TF, and CP after i.v. injection were 3.37+/-0.63, 2.43+/-0.29, and 2.12+/-0.21 h, respectively. The mean values of Varea for FF (1.39+/-0.31 L/kg) and TP (1.31+/-0.19 L/kg) were similar, but significantly different from that of CP (1.04+/-0.12 L/kg). The bioavailabilities of FF, TP, and CP after oral administration were 82%, 69%, and 45%, respectively. Differences in the bioavailability values of the compared fenicol antibiotics correspond to the ratio of the apolar/polar surface areas of their particles.

[Plant protein kinases stimulated by calcium]

Calcium signals play an important role in many aspects of plant growth and development, including plant response to biotic and abiotic stress. The stimulus characteristic intracellular Ca2+ signals are generated in plant cells by a variety of stimuli, including changes in environmental conditions, interaction with microbes and growth and development processes. Cytoplasmatic calcium brings about responses by interacting with target proteins, like calcium-dependent kinases. In plant there are at least five classes of protein kinases (CDPK, CRK, CCaMK, CaMK and SnRK3), which activity is regulated by calcium ions. In this article the structure, regulation and function of calcium stimulated protein kinases are briefly reviewed.

A receptor-like kinase from Arabidopsis thaliana is a calmodulin-binding protein

Screening a cDNA expression library with a radiolabelled calmodulin (CaM) probe led to the isolation of AtCaMRLK, a receptor-like kinase (RLK) of Arabidopsis thaliana. AtCaMRLK polypeptide sequence shows a modular organization consisting of the four distinctive domains characteristic of receptor kinases: an amino terminal signal sequence, a domain containing seven leucine-rich repeats, a single putative membrane-spanning segment and a protein kinase domain. Using truncated versions of the protein and a synthetic peptide, we demonstrated that a region of 23 amino acids, located near the kinase domain of AtCaMRLK, binds CaM in a calcium-dependent manner. Real-time binding experiments showed that AtCaMRLK interacted in vitro with AtCaM1, a canonical CaM, but not with AtCaM8, a divergent isoform of the Ca2+ sensor. The bacterially expressed kinase domain of the protein was able to autophosphorylate and to phosphorylate the myelin basic protein, using Mn2+ preferentially to Mg2+ as an ion activator. Site-directed mutagenesis of the conserved lysine residue (Lys423) to alanine, in the kinase subdomain II, resulted in a complete loss of kinase activity. CaM had no influence on the autophosphorylation activity of AtCaMRLK. AtCaMRLK was expressed in reproductive and vegetative tissues of A. thaliana, except in leaves. Disruption in the AtCaMRLK coding sequence by insertion of a DsG transposable element in an Arabidopsis mutant did not generate a discernible phenotype. The CaM-binding motif of AtCaMRLK was found to be conserved in several other members of the plant RLK family, suggesting a role for Ca2+/CaM in the regulation of RLK-mediated pathways.

The involvement of cyclic GMP in the photoperiodic flower induction of Pharbitis nil

The involvement of cGMP in the regulation of the flowering of Pharbitis nil was investigated through exogenous applications of cGMP and chemicals that are able to change the cGMP level and analyses of endogenous cGMP level. Exogenous applications of cGMP and 8-pCPT-cGMP (a cyclic GMP non hydrolyzed analog) to P. nil plants, which were exposed to a 12-h-long subinductive night, significantly increased flowering response. NS-2028 (guanylyl cyclase inhibitor) inhibited flowering when that compound was applied during a 16-h-long inductive night, whereas SNP (guanylyl cyclase activator) increased the flowering when plants were subjected to a 12-h-long subinductive night. The inhibitors of cyclic nucleotides phosphodiesterase (isobutyl-methylxanthine and dipyridamole), which increase the cytosolic cGMP level, promoted the flowering and allowed the length of the dark period necessary for induction of flowering to be reduced. The endogenous cGMP level was also measured after the treatment of P. nil seedlings with those chemicals. Results have clearly shown that compounds that were used in physiological experiments modulated endogenous cGMP level. There was a significant difference in the cyclic GMP level between 16-h-long night conditions and a long night with a night-break. During a long inductive night the oscillation of cGMP was observed with four main peaks in 4, 7, 11, 14 h, whereas a 10 min flash of red light in the middle of the night was able to modify these rhythmical changes in the second half of the long night. These results have shown that there are oscillations in the concentration of cGMP in the night and the biosynthesis and/or deactivation of cGMP is affected by light treatment and therefore it may be involved in the regulation of photoinduction processes in cotyledons. From these combined results, we propose a hypothesis that cGMP is involved in the control of photoperiodic flower induction in Pharbitis nil.

Biochemical evidence for a cGMP-regulated protein kinase in Pharbitis nil

It is known that the level of cGMP is modulated in response to a number of stimuli in plant cells but intracellular events distal to cGMP metabolism are not clear. Cyclic GMP-dependent protein kinase (Pk-G) is a major effector of cGMP action in animals and yeasts. We wanted to determine whether such kinase is present in plant cells. A soluble protein kinase was isolated from seedlings of Pharbitis nil and purified following purification methods including anion-exchange and affinity-chromatography. The enzyme consists of a single polypeptide of M(r) 70 kDa as determined by SDS-PAGE. From conventional modulators only cyclic GMP, when applied in low concentration, was able to accelerate the enzyme activity in the presence of histones. The enzyme autophosphorylated on serine and threonine residues and phosphorylated some substrates only on serine residues. Mixture of histones and histones H2B, H3 were the best phosphate acceptors. The process of autophosphorylation was accelerated by a low concentration of cGMP and reduced by high concentration of this second messenger. Antibodies raised against catalytic domain of animals Pk-G I alpha and beta cross-reacted with protein kinase from Pharbitis nil tissue. These data, taken together, demonstrate the presence of functional enzyme, which activity is regulated by cGMP and allow to classify this protein kinase as a member of the second messenger regulated group of enzymes.

Biochemical evidence for a calcium-dependent protein kinase from Pharbitis nil and its involvement in photoperiodic flower induction

A soluble Ca(2+)-dependent protein kinase (CDPK) was isolated from seedlings of the short-day plant Pharbitis nil and purified to homogeneity. Activity of Pharbitis nil CDPK (PnCDPK) was strictly dependent on the presence of Ca(2+) (K(0,5)=4,9 microM). The enzyme was autophosphorylated on serine and threonine residues and phosphorylated a wide diversity of substrates only on serine residues. Histone III-S and syntide-2 were the best phosphate acceptors (K(m) for histone III-S=0,178 mg ml(-1)). Polyclonal antibodies directed to a regulatory region of the soybean CDPK recognized 54 and 62 kDa polypeptides from Pharbitis nil. However, only 54 kDa protein was able to catalyse autophosphorylation and phosphorylation of substrates in a Ca(2+)-dependent manner. CDPK autophosphorylation was high in 5-day-old Pharbitis nil seedlings grown under non-inductive continuous white light and was reduced to one-half of its original when plants were grown in the long inductive night. Also, the pattern of proteins phosphorylation has changed. After 16-h-long inductive night phosphorylation of endogenous target (specific band of 82 kDa) increased in the presence of calcium ions. It may suggest that Ca(2+)-dependent protein kinase is involved in this process and it is dependent on light/dark conditions.