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Homologous Domains (homologous + domain)
Selected AbstractsMutations in JAK2V617F homologous domain of JAK genes are uncommon in solid tumorsINTERNATIONAL JOURNAL OF CANCER, Issue 9 2007Nelly Motté No abstract is available for this article. [source] Combined use of selective inhibitors and fluorogenic substrates to study the specificity of somatic wild-type angiotensin-converting enzymeFEBS JOURNAL, Issue 8 2006Nicolas D. Jullien Somatic angiotensin-converting enzyme (ACE) contains two homologous domains, each bearing a functional active site. Studies on the selectivity of these ACE domains towards either substrates or inhibitors have mostly relied on the use of mutants or isolated domains of ACE. To determine directly the selectivity properties of each ACE domain, working with wild-type enzyme, we developed an approach based on the combined use of N-domain-selective and C-domain-selective ACE inhibitors and fluorogenic substrates. With this approach, marked differences in substrate selectivity were revealed between rat, mouse and human somatic ACE. In particular, the fluorogenic substrate Mca-Ala-Ser-Asp-Lys-DpaOH was shown to be a strict N-domain-selective substrate of mouse ACE, whereas with rat ACE it displayed marked C-domain selectivity. Similar differences in selectivity between these ACE species were also observed with a new fluorogenic substrate of ACE, Mca-Arg-Pro-Pro-Gly-Phe-Ser-Pro-DpaOH. In support of these results, changes in amino-acid composition in the binding site of these three ACE species were pinpointed. Together these data demonstrate that the substrate selectivity of the N-domain and C-domain depends on the ACE species. These results raise concerns about the interpretation of functional studies performed in animals using N-domain and C-domain substrate selectivity data derived only from human ACE. [source] Purification, characterization, and cDNA cloning of a novel soluble saxitoxin and tetrodotoxin binding protein from plasma of the puffer fish, Fugu pardalisFEBS JOURNAL, Issue 22 2001Mari Yotsu-Yamashita Some species of puffer fish have been reported to possess both of tetrodotoxin and saxitoxin, which share one binding site on sodium channels. We purified a novel soluble glycoprotein that binds to these toxins from plasma of the puffer fish, Fugu pardalis, and named puffer fish saxitoxin and tetrodotoxin binding protein (PSTBP). PSTBP possessed a binding capacity of 10.6 ± 0.97 nmol·mg,1 protein and a Kd of 14.6 ± 0.33 nm for [3H]saxitoxin in equilibrium binding assays. [3H]Saxitoxin (10 nm) binding to PSTBPs was half-inhibited by the presence of tetrodotoxin and saxitoxin at 12 µm and 8.5 nm, respectively. From the results of gel filtration chromatography (200 kDa) and SDS/PAGE (104 kDa), PSTBP was suggested to consist of noncovalently linked dimers of a single subunit. PSTBP was completely deglycosylated by glycopeptidase F, producing a single band at 42 kDa. Two highly homologous cDNAs to each other coding PSTBP (PSTBP1 and PSTBP2, the predicted amino-acid identity 93%), were obtained from a cDNA library of F. pardalis liver. These proteins consisted to two tandemly repeated homologous domains. The predicted amino-acid sequences of PSTBP1 and 2 were not homologous to that of saxiphilin, a reported saxitoxin binding protein, or sodium channels, but their N-terminus sequences were homologous to that of the reported tetrodotoxin binding protein from plasma of Fugu niphobles, which has not been fully characterized. The partially homologous cDNA sequences to PSTBP1 and 2 were also found in expressed sequence tag clones of nontoxic flounders liver. Presumably, PSTBP is involved in accumulation and/or excretion of toxins in puffer fish. [source] A novel repressor of nif and glnA expression in the methanogenic archaeon Methanococcus maripaludisMOLECULAR MICROBIOLOGY, Issue 1 2003Thomas J. Lie Summary Nitrogen assimilation in the methanogenic archaeon Methanococcus maripaludis is regulated by transcriptional repression involving a palindromic ,nitrogen operator' repressor binding sequence. Here we report the isolation of the nitrogen repressor, NrpR, from M. maripaludis using DNA affinity purification. Deletion of the nrpR gene resulted in loss of nitrogen operator binding activity in cell extracts and loss of repression of nif (nitrogen- fixation) and glnA (glutamine synthetase) gene expression in vivo. Genetic complementation of the nrpR mutation restored all functions. NrpR contained a putative N-terminal winged helix,turn,helix motif followed by two mutually homologous domains of unknown function. Comparison of the migration of NrpR in gel-filtration chromatography with its subunit molecular weight (60 kDa) suggested that NrpR was a tetramer. Several lines of evidence suggested that the level of NrpR itself is not regulated, and the binding affinity of NrpR to the nitrogen operator is controlled by an unknown mechanism. Homologues of NrpR were found only in certain species in the kingdom Euryarchaeota. Full length homologues were found in Methanocaldococcus jannaschii and Methanothermobacter thermoautotrophicus, and homologues lacking one or more of the three polypeptide domains were found in Archaeoglobus fulgidus, Methanopyrus kandleri, Methanosarcina acetivorans, and Methanosarcina mazei. NrpR represents a new family of regulators unique to the Euryarchaeota. [source] Sugar-complex structures of the C-half domain of the galactose-binding lectin EW29 from the earthworm Lumbricus terrestrisACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2009Ryuichiro Suzuki R-type lectins are one of the most prominent types of lectin; they exist ubiquitously in nature and mainly bind to the galactose unit of sugar chains. The galactose-binding lectin EW29 from the earthworm Lumbricus terrestris belongs to the R-type lectin family as represented by the plant lectin ricin. It shows haemagglutination activity and is composed of a single peptide chain that includes two homologous domains: N-terminal and C-terminal domains. A truncated mutant of EW29 comprising the C-terminal domain (rC-half) has haemagglutination activity by itself. In order to clarify how rC-half recognizes ligands and shows haemagglutination activity, X-ray crystal structures of rC-half in complex with d -lactose and N -acetyl- d -galactosamine have been determined. The structure of rC-half is similar to that of the ricin B chain and consists of a ,-trefoil fold; the fold is further divided into three similar subdomains referred to as subdomains ,, , and ,, which are gathered around the pseudo-threefold axis. The structures of sugar complexes demonstrated that subdomains , and , of rC-half bind terminal galactosyl and N -acetylgalactosaminyl glycans. The sugar-binding properties are common to both ligands in both subdomains and are quite similar to those of ricin B chain,lactose complexes. These results indicate that the C-terminal domain of EW29 uses these two galactose-binding sites for its function as a single-domain-type haemagglutinin. [source] | ||||||||||