Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.13.3 (histidine kinase)
 2,405 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A previous method for red cell fractionation by density gradient centrifugation, using a swing-out rotor, has been scaled up to deal with larger volumes of red cells. This method, involving the use of a zonal rotor, is described and has been applied to the study of the decay of hexokinase in the red cells of normal individuals. Hexokinase activity was seen to fall very rapidly in the young cells followed by a much more gradual decline in older cells. It is estimated that the mature red cell probably contains no more than 2-3% of the hexokinase activity originally present in the reticulocyte. An electrophoretic study showed a changing pattern of the isozymes HK1 and HK2 with increasing cell age. HK2 declines very rapidly in the early fractions whereas HK1 appears to decay more gradually.
 ...
PMID:An examination of the age-related patterns of decay of the hexokinases of human red cells. 120 20

An electrophoretic system which gives a clear separation of human hexokinases HK1, HK2 and HK3 is described. The distribution of the hexokinase isozymes in various human tissues, both adult and fetal, is reported. Some properties of the isozymes were investigated. HK2 was found to be more thermolabile than HK1, and there was also a small but significant difference in molecular size. Unlike HK3, HK1 and HK2 are not inhibited by high glucose concentrations. Screening of red cell lysates from 800 unrelated European individuals revealed no genetic variants of HK1 and HK2. However, in view of their difference in properties, it seems probable that the HK1 and HK2 isozymes are determined by separate gene loci.
 ...
PMID:An electrophoretic study of the distribution and properties of human hexokinases. 123 74

K+ channels represent the most complex class of voltage-gated ion channels from both functional and structural standpoints. In the heart these channels are responsible for the rapid repolarizing phases of the action potential and are the targets of several antiarrhythmic drugs. Full-length cDNA clones were isolated from human ventricular libraries that encode two voltage-gated K+ channels. These two cDNAs, designated HK1 and HK2, encode proteins of 653 and 605 amino acids, respectively. HK1 is the human equivalent (98% identity) of an inactivating K+ channel previously described in rat heart (RHK1) whereas the HK2 channel is 86% identical to a cloned rat brain K+ channel (Kv1). The only amino acid sequence identity (72%) between HK1 and HK2 is within the central region containing the membrane spanning domains. Northern blot analysis of human mRNA indicated that HK1 is slightly more abundant in ventricle than atrium whereas HK2 is much more abundant in atrium relative to ventricle. Both channel transcripts are present in ventricle at levels equivalent to voltage-gated Na+ channels. Analysis of the gene encoding HK1 suggests the coding sequence is intronless and is represented once in the human genome.
 ...
PMID:Molecular cloning and characterization of two voltage-gated K+ channel cDNAs from human ventricle. 200 94

Ca2+-ATPase molecules present in the microsomal fraction from non-muscle cells were examined immunologically. Rabbit whole brain, cerebellum, liver, kidney, and COS-1 cell microsomes all displayed a polypeptide of about 110 kDa which was immunoreactive with a polyclonal antiserum against the cardiac muscle sarcoplasmic reticulum Ca2+-ATPase molecule, but was not immunoreactive with a monoclonal antibody specific for the fast-twitch muscle Ca2+-ATPase. cDNAs encoding the full length of two Ca2+-ATPase molecules were isolated from a human kidney library using a mixture of nucleotide probes derived from both rabbit fast-twitch and cardiac muscle Ca2+-ATPase cDNAs. The human kidney cDNAs, HK1 and HK2, are the products of alternative splicing. HK2 codes for a protein identical to rabbit cardiac muscle Ca2+-ATPase, with the exception of 6 scattered amino acid replacements, whereas HK1 codes for a protein identical to that encoded by HK2, but with the carboxyl-terminal 4 amino acids replaced by an extended sequence of 49 amino acids. cDNAs of the HK1 type are by far the most abundant in the library. The partial structure of a 40-kilobase genomic DNA encoding all but the 5' end of the human cardiac Ca2+-ATPase is described. The exons which give rise to the alternatively spliced products were located by Southern blotting and sequencing, and the alternative splicing patterns were determined.
 ...
PMID:Molecular cloning of cDNAs from human kidney coding for two alternatively spliced products of the cardiac Ca2+-ATPase gene. 284 96

Hexose kinases in rice embryos have been characterized. Six isoforms were detected: i.e. three glucokinases (GK1-3), two hexokinases (HK1 and HK2) and one fructokinase (FK1). Out of these, GK3, HK1 and HK2 were inhibited by mannoheptulose and glucosamine, known inhibitors of hexokinase activity. These inhibitors are also known to be modulators of sugar sensing processes. The results suggest that GK3, HK1 and HK2 may play a role in sensing the cellular sugar status in the rice embryo.
 ...
PMID:Characterization of isoforms of hexose kinases in rice embryo. 1068 Jan 71

Hydroxyketone chelators, deferiprone (HK1), maltol (HK3) and their related compounds (HK2, 4-8), were characterized for their cytotoxic profiles against oral human normal and tumor cells. Most hydroxyketones except HK6 showed relatively higher tumor-specific cytotoxicity. Deferiprone (HK1), which showed the highest tumor specificity, had 10 times higher cytotoxicity than maltol (HK3) in both human promyelocytic leukemia HL-60 and human oral squamous cell carcinoma HSC-2 cell lines. The cytotoxic activity of HK1 against HL-60 and HSC-2 cells was reduced in the presence of FeCl3, while that of HK3 was significantly increased by FeCl3. Agarose gel electrophoresis showed that HK1 induced internucleosomal DNA fragmentation in HL-60 cells, but the addition of FeCl3 inhibited the DNA fragmentation. HK3 did not induce DNA fragmentation in HL-60 cells, regardless of the presence or absence of FeCl3. In HSC-2 cells, HK1 and 3 did not induce DNA fragmentation in the presence or absence of FeCl3. Colorimetric protease assay showed that HK1 activated the caspase 3, 8 and 9 in HL-60 cells. On the other hand, HK3 did not activate the caspase 3, 8 and 9 in HL-60 cells, but activated the caspase 3 only slightly in the presence of FeCl3. HK1 and 3 also activated the caspase 3, 8 and 9 in HSC-2 cells, but to a lesser extent. The present study suggested that the antitumor activity of hydroxyketones may be modified by Fe3+ concentration.
 ...
PMID:Cytotoxic activity of deferiprone, maltol and related hydroxyketones against human tumor cell lines. 1516 Oct 23

Two-component systems (TCSs) are the major signalling pathway in bacteria and represent potential drug targets. Among the 11 paired TCS proteins present in Mycobacterium tuberculosis H37Rv, the histidine kinases (HKs) Rv0600c (HK1) and Rv0601c (HK2) are annotated to phosphorylate one response regulator (RR) Rv0602c (TcrA). We wanted to establish the sequence-structure-function relationship to elucidate the mechanism of phosphotransfer using in silico methods. Sequence alignments and codon usage analysis showed that the two domains encoded by a single gene in homologous HKs have been separated into individual open-reading frames in M. tuberculosis. This is the first example where two incomplete HKs are involved in phosphorylating a single RR. The model shows that HK2 is a unique histidine phosphotransfer (HPt)-mono-domain protein, not found as lone protein in other bacteria. The secondary structure of HKs was confirmed using "far-UV" circular dichroism study of purified proteins. We propose that HK1 phosphorylates HK2 at the conserved H131 and the phosphoryl group is then transferred to D73 of TcrA.
 ...
PMID:Functional insights from the molecular modelling of a novel two-component system. 1665 Aug 22

A unique three protein two-component system is present in Mycobacterium tuberculosis comprising of two histidine kinases (Rv0600c/HK1 and Rv0601c/HK2) and a response regulator (Rv0602c/TcrA). The HK2 is a novel HPt-mono domain protein absent in other bacteria. We present here the temperature and urea induced denaturation study of HK1 and HK2 using circular dichroism and fluorescence spectroscopy. HK1 and HK2 are thermally quite stable. Thermal transition of HK1 is a two-state process and that of HK2 is a three-state process. Urea denaturation of HK1 and HK2 is a three-state and two-state process, respectively. The DeltaG degrees of the two transitions during urea induced unfolding of HK1 is 4.76+/-0.6 kcal/mol and -7.11+/-0.8 kcal/mol. Unfolding of HK2 in presence of urea has DeltaG degrees of 4.766+/-0.5 kcal/mol. The intrinsic fluorescence study of HK2 unfolding implies flexibility of proline rich loop in the tryptophan bearing HAMP domain.
 ...
PMID:Temperature and urea induced conformational changes of the histidine kinases from Mycobacterium tuberculosis. 1733 92

The two-component signal transduction system from Mycobacterium tuberculosis bears a unique three-protein system comprising of two putative histidine kinases (HK1 and HK2) and one response regulator TcrA. By sequence analysis, HK1 is found to be an adenosine 5'-triphosphate (ATP) binding protein, similar to the nucleotide-binding domain of homologous histidine kinases, and HK2 is a unique histidine containing phosphotransfer (HPt)-mono-domain protein. HK1 is expected to interact with and phosphorylate HK2. Here, we show that HK1 binds 2'(3')-O-(2,4,6-trinitrophenyl)adenosine 5'-triphosphate monolithium trisodium salt and ATP with a 1:1 stoichiometric ratio. The ATPase activity of HK1 in the presence of HK2 was measured, and phosphorylation experiments suggested that HK1 acts as a functional kinase and phosphorylates HK2 by interacting with it. Further phosphorylation studies showed transfer of a phosphoryl group from HK2 to the response regulator TcrA. These results indicate a new mode of interaction for phosphotransfer between the two-component system proteins in bacteria.
 ...
PMID:Probing the nucleotide binding and phosphorylation by the histidine kinase of a novel three-protein two-component system from Mycobacterium tuberculosis. 1743 92

Hexokinase is the first enzyme in the glycolytic pathway and utilizes ATP to convert glucose to glucose-6-phosphate (G6P). We previously identified three variant transcripts of Hk1 that are expressed specifically in spermatogenic cells, have different 5' untranslated regions, and encode a protein (HK1S, spermatogenic cell-specific type 1 hexokinase) in which the porin-binding domain (PBD) of HK1 is replaced by a novel N-terminal spermatogenic cell-specific region (SSR). However, the level of expression of the individual variant transcripts or of the other members of the hexokinase gene family (Hk2, Hk3, and Gck) in spermatogenic cells remains uncertain. We show that Hk1, Hk2, and Hk3 transcripts levels are quite low in spermatocytes and spermatids and Gck transcripts are relatively abundant in spermatids, but that glucokinase (GCK) is not detected in spermatozoa. Using real time RT-PCR (qPCR) with primers specific for each of the three variant forms and RNA from whole testis and isolated germ cells, we found that transcripts for Hk1_v2 and Hk1_v3, but not for Hk1_v1, are relatively high in spermatids. Similar results were seen using spermatogenic cells isolated by laser-capture microdissection (LCM). Immunoblotting studies found that HK1S is abundant in sperm, and immunostaining confirmed that HK1S is located mainly in the principal piece of the sperm flagellum, where other spermatogenic cell-specific glycolytic enzymes have been found. These results strongly suggest that HK1, HK2, HK3, and GCK are unlikely to have a role in glycolysis in sperm and that HK1S encoded by Hk1_v2 and Hk1_v3 serves this role.
 ...
PMID:Spermatogenic cell-specific type 1 hexokinase is the predominant hexokinase in sperm. 1792


1 2 3 Next >>