Search results for "Structural Biology."
showing 10 items of 822 documents
Binding and/or hydrolysis of purine‐based nucleotides is not required for IM30 ring formation
2021
IM30, the inner membrane-associated protein of 30 kDa, is conserved in cyanobacteria and chloroplasts. Although its exact physiological function is still mysterious, IM30 is clearly essential for thylakoid membrane biogenesis and/or dynamics. Recently, a cryptic IM30 GTPase activity has been reported, albeit thus far no physiological function has been attributed to this. Yet, it is still possible that GTP binding/hydrolysis affects formation of the prototypical large homo-oligomeric IM30 ring and rod structures. Here, we show that the Synechocystis sp. PCC 6803 IM30 protein in fact is an NTPase that hydrolyzes GTP and ATP, but not CTP or UTP, with about identical rates. While IM30 forms lar…
Ras-pathway has a dual role in yeast galactose metabolism
2007
AbstractIn the yeast Saccharomyces cerevisiae the genes involved in galactose metabolism (GAL1,7,10) are transcriptionally activated more than a 1000-fold in the presence of galactose as the sole carbon source in the culture media. In the present work, we monitored the activity of the GAL10 gene promoter in different Ras-cAMP genetic backgrounds. We demonstrate that overexpression of C-terminus of the nucleotide exchange factor Cdc25p stimulates GAL10 transcription in yeast strains carrying the contemporary deletion of both RAS genes. Moreover, the deletion of the chromosomal CDC25 gene provokes impaired growth on galactose based media in yeast strain lacking both RAS genes and adenylate cy…
Keyhole limpet haemocyanin (KLH): Purification of intact KLH1 through selective dissociation of KLH2
1995
Abstract Keyhole limpet haemocyanin (KLH) from almost all newly captive animals contains a mixture of KLH1 and KLH2. We show that the dissociation of KLH2 can be produced during EM specimen preparation by the negative staining-carbon film (NS-CF) procedure and in solution by ammonium molybdate-PEG solutions at slightly acidic pHs. The KLH2 multidecamers split apart in the pH range 7.5-6.5 and in the pH range 6.5-6.0 the individual decamers break open and start to dissociate. At pH 5.9 the dissociation of KLH2 yields predominantly a mixture of single subunits and what appear to be subunit dimers. Over the pH range 7.0-5.7 the KLH1 didecamer remains stable. Separation of intact KLH1, in the f…
Development of injectable and durable kefiran hydro-alcoholic gels.
2020
Injectable, in-situ forming kefiran gels have been developed for potential applications as implantable drug delivery devices or scaffolds for tissue regeneration. Concentrated solutions (4, 5 and 6%w) of kefiran, extracted from kefir grains, have been assessed in term of viscosity and injectability through G26 syringe needles, and for their ability to undergo gelation upon mixing with different alcohols. Propylene glycol (PG) has been selected as gelling agent because it ensures homogenous gelation in relatively short times (from few minutes up to 6 h). The investigation of the rheological behavior of kefiran/PG gels varying polymer concentration and temperature (25 degrees C and 37 degrees…
Crystal Structure of the Maturation Protein from Bacteriophage Qβ
2017
Abstract Virions of the single-stranded RNA bacteriophages contain a single copy of the maturation protein, which is bound to the phage genome and is required for the infectivity of the particles. The maturation protein mediates the adsorption of the virion to bacterial pili and the subsequent release and penetration of the genome into the host cell. Here, we report a crystal structure of the maturation protein from bacteriophage Qβ. The protein has a bent, highly asymmetric shape and spans 110 A in length. Apart from small local substructures, the overall fold of the maturation protein does not resemble that of other known proteins. The protein is organized in two distinct regions, an α-he…
Dynamics of gene regulatory networks and their dependence on network topology and quantitative parameters – the case of phage λ
2019
Background Gene regulatory networks can be modelled in various ways depending on the level of detail required and biological questions addressed. One of the earliest formalisms used for modeling is a Boolean network, although these models cannot describe most temporal aspects of a biological system. Differential equation models have also been used to model gene regulatory networks, but these frameworks tend to be too detailed for large models and many quantitative parameters might not be deducible in practice. Hybrid models bridge the gap between these two model classes – these are useful when concentration changes are important while the information about precise concentrations and binding…
Origin of the interferon-inducible (2′-5′)oligoadenylate synthetases: cloning of the (2′-5′)oligoadenylate synthetase from the marine spongeGeodia cy…
1999
In vertebrates cytokines mediate innate (natural) immunity and protect them against viral infections. The cytokine interferon causes the induction of the (2′-5′)oligoadenylate synthetase [(2-5)A synthetase], whose product, (2′-5′)oligoadenylate, activates the endoribonuclease L which in turn degrades (viral) RNA. Three isoforms of (2-5)A synthetases exist, form I (40–46 kDa), form II (69 kDa), and form III (100 kDa). Until now (2-5)A synthetases have only been cloned from birds and mammals. Here we describe the cloning of the first putative invertebrate (2-5)A synthetase from the marine sponge Geodia cydonium. The deduced amino acid sequence shows signatures characteristic for (2-5)A synthe…
Differential sensitivity of rat hepatocyte CYP isoforms to self-generated nitric oxide.
2001
AbstractEarly loss of P450 in rat hepatocyte cultures appears directly related to nitric oxide (NO) overproduction. This study investigates the influence of endogenously generated NO (or NO-derived species) on the relative expression of cytochrome P450 (CYP) isoforms in rat hepatocytes. Our results support the view that loss of P450 holoenzyme in culture is the ultimate consequence of a NO driven process, activated during the common hepatocyte isolation procedure, that leads to an accelerated and selective degradation of specific CYP apoproteins. Under conditions in which NO and peroxynitrite formation is operative, changes in the level of specific CYP isoforms result in a significant alter…
The b1 isoform of protocadherin-gamma (Pcdhgamma) interacts with the microtubule-destabilizing protein SCG10.
2004
Due to their structural characteristics and their diversity, the 22 members of the protocadherin-gamma (Pcdhgamma) family have been suggested to contribute to the establishment of specific connections in the nervous system. Here, we focus on a single isoform, Pcdhgamma-b1. Its expression is found in different brain regions and in developing spinal cord it is restricted to scattered cells, whereas all cells are labeled using an antibody that recognizes all Pcdhgamma isoforms. As a first step to understanding the signaling mechanisms downstream of Pcdhgamma, we identify the microtubule-destabilizing protein SCG10 as a cytoplasmic interactor for Pcdhgamma-b1 and other isoforms of the Pcdhgamma…
Expression of retinoic acid nuclear receptors in the mouse embryonal carcinoma cell line PCC7-Mz1
1992
Mouse embryonal carcinoma cell line PCC7-Mz1 can serve as a model of mammalian neural development [1989, J. Cell. Biol. 109, 2481-2493]. Upon exposure to all-trans retinoic acid (RA), Mz1 cells differentiate into a stable pattern of neurons, astroglia and fibroblasts whereas variants of the parental cell line either are restricted in their patterns of derivatives or do not respond at all to RA. Using gene probes specific for the alpha 1, alpha 2 and beta 2 isoforms of the retinoic acid nuclear receptor, we have studied by Northern blot analysis the expression of these transcription factors in uninduced and induced cells of clone Mz1 and in variants with different developmental potential. al…