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71.
Elastin, the protein responsible for tissue elasticity, is contained in arterial walls, lungs, and skin. Given the cassette like organization of the human tropoelastin gene, giving rise to alternating exons encoding for crosslink domains and elastomeric domains, it is tempting to suggest that polypeptides encoded by different exons could adopt structures independent of the other exons. The results obtained with the polypeptide sequences encoded by exons 3, 7, and 30 of human tropoelastin are described. It is shown that these hydrophobic exons may partly assume the polyproline II (PPII) structure, as found by circular dichroism studies in aqueous solution. Classical Raman spectroscopy evidences a specific sharp band at 1314 cm(-1), which is assigned to the PPII structure adopted by these exons in the solid state. As these sequences are among those putatively responsible for elastomeric properties, these findings are of particular interest in relation to the current models of the elasticity of elastin. 相似文献
72.
73.
Anna?Lobley Valerie?Pierron Lindsey?Reynolds Liz?Allen David?MichalovichEmail author 《Reproductive biology and endocrinology : RB&E》2003,1(1):53
Background
CatSper1 and CatSper2 are two recently identified channel-like proteins, which show sperm specific expression patterns. Through targeted mutagenesis in the mouse, CatSper1 has been shown to be required for fertility, sperm motility and for cAMP induced Ca2+ current in sperm. Both channels resemble a single pore forming repeat from a four repeat voltage dependent Ca2+ /Na+ channel. However, neither CatSper1 or CatSper2 have been shown to function as cation channels when transfected into cells, singly or in conjunction. As the pore forming units of voltage gated cation channels form a tetramer it has been suggested that the known CatSper proteins require additional subunits and/or interaction partners to function. 相似文献74.
75.
We previously mapped early-activated replication origins in the promoter regions of five abundantly transcribed genes in the slime mold Physarum polycephalum. This physical linkage between origins and genes is congruent with the preferential early replication of the active genes in mammalian cells. To determine how general this replicational organization is in the synchronous plasmodium of Physarum, we analyzed the replication of three weakly expressed genes. Bromodeoxyuridine (BrdUrd) density-shift and gene dosage experiments indicated that the redB (regulated in development) and redE genes replicate early, whereas redA replicates in mid-S phase. Bi-dimensional gel electrophoresis revealed that redA coincides with an origin that appears to be activated within a large temporal window in S phase so that the replication of the gene is not well defined temporally. The early replication of the redB and redE genes is due to the simultaneous activation of flanking origins at the onset of S phase. As a result, these two genes correspond to termination sites of DNA replication. Our data demonstrate that not all the Physarum promoters are preferred sites of initiation but, so far, all the expressed genes analyzed in detail either coincide with a replication origin or are embedded into a cluster of early firing replicons. 相似文献
76.
VanBuren P Alix SL Gorga JA Begin KJ LeWinter MM Alpert NR 《American journal of physiology. Heart and circulatory physiology》2002,282(5):H1665-H1671
Alteration of troponin T (TnT) isoform expression has been reported in human and animal models of myocardial failure. The two adult beef cardiac TnT isoforms (TnT(3) and TnT(4)) were isolated for comparative functional analysis. Thin filaments were reconstituted containing pure populations of the isoforms. The in vitro motility assay was used to directly compare the effect of the two TnT isoforms on force and unloaded shortening as a function of free calcium. We found no significant differences between the two isoforms in terms of calcium sensitivity, cooperativity, or maximal activation (velocity and force) as assessed in a fully calcium-regulated system. Activation by myosin strong binding was similar for thin filaments containing either of the two TnT isoforms. Whereas maximally activated velocity and cooperativity was depressed at pH 6.5, no difference between thin filaments containing the two isoforms was detected. From the small magnitude of the TnT isoform shifts detected in myocardial failure and the lack of significant mechanical effect detected in the motility assay, variable TnT isoform expression is unlikely to be any functional significance in heart failure. 相似文献
77.
In the central nervous system of both vertebrates and invertebrates inhibitory neurotransmission is mainly achieved through activation of γ-aminobutyric acid (GABA) receptors. Extensive studies have established the structural and pharmacological properties of vertebrate GABA receptors. Although the vast majority of insect GABA-sensitive responses share some properties with vertebrate GABAA receptors, peculiar pharmacological properties of these receptors led us to think that several GABA-gated chloride channels are present in insects. We describe here the pharmacological properties of two GABA receptor subtypes coupled to a chloride channel on dorsal unpaired median (DUM) neurones of the adult male cockroach. Long applications of GABA induce a large biphasic hyperpolarization, consisting of an initial transient hyperpolarization followed by a slow phase of hyperpolarization that is not quickly desensitized. With GABA, the transient hyperpolarization is sensitive to picrotoxinin, fipronil and dieldrin whereas the slow response is insensitive to these insecticides.When GABA is replaced by muscimol and cis-4-aminocrotonic acid (CACA) a biphasic hyperpolarization consisting of an initial transient hyperpolarization followed by a sustained phase is evoked which is blocked by picrotoxinin and fipronil. Exposure to dieldrin decreases only the early phase of the muscimol and CACA-induced biphasic response, suggesting that two GABA-gated chloride channel receptor subtypes are present in DUM neurones. This study describes, for the first time, a dieldrin resistant component different to the dieldrin- and picrotoxinin-resistant receptor found in several insect species. 相似文献
78.
Hugo Schweke Qifang Xu Gerardo Tauriello Lorenzo Pantolini Torsten Schwede Frédéric Cazals Alix Lhéritier Juan Fernandez-Recio Luis Angel Rodríguez-Lumbreras Ora Schueler-Furman Julia K. Varga Brian Jiménez-García Manon F. Réau Alexandre M. J. J. Bonvin Castrense Savojardo Pier-Luigi Martelli Rita Casadio Jérôme Tubiana Haim J. Wolfson Romina Oliva Didier Barradas-Bautista Tiziana Ricciardelli Luigi Cavallo Česlovas Venclovas Kliment Olechnovič Raphael Guerois Jessica Andreani Juliette Martin Xiao Wang Genki Terashi Daipayan Sarkar Charles Christoffer Tunde Aderinwale Jacob Verburgt Daisuke Kihara Anthony Marchand Bruno E. Correia Rui Duan Liming Qiu Xianjin Xu Shuang Zhang Xiaoqin Zou Sucharita Dey Roland L. Dunbrack Emmanuel D. Levy Shoshana J. Wodak 《Proteomics》2023,23(17):2200323
Reliably scoring and ranking candidate models of protein complexes and assigning their oligomeric state from the structure of the crystal lattice represent outstanding challenges. A community-wide effort was launched to tackle these challenges. The latest resources on protein complexes and interfaces were exploited to derive a benchmark dataset consisting of 1677 homodimer protein crystal structures, including a balanced mix of physiological and non-physiological complexes. The non-physiological complexes in the benchmark were selected to bury a similar or larger interface area than their physiological counterparts, making it more difficult for scoring functions to differentiate between them. Next, 252 functions for scoring protein-protein interfaces previously developed by 13 groups were collected and evaluated for their ability to discriminate between physiological and non-physiological complexes. A simple consensus score generated using the best performing score of each of the 13 groups, and a cross-validated Random Forest (RF) classifier were created. Both approaches showed excellent performance, with an area under the Receiver Operating Characteristic (ROC) curve of 0.93 and 0.94, respectively, outperforming individual scores developed by different groups. Additionally, AlphaFold2 engines recalled the physiological dimers with significantly higher accuracy than the non-physiological set, lending support to the reliability of our benchmark dataset annotations. Optimizing the combined power of interface scoring functions and evaluating it on challenging benchmark datasets appears to be a promising strategy. 相似文献
79.
Methylated amino acids in ribosomal proteins from Escherichia coli treated with ethionine and from a mutant lacking methylation of protein L11. 总被引:2,自引:0,他引:2
In the present study, the nature, proportions and distribution of methylated amino acids in ribosomal proteins from Escherichia coli grown in the presence of ethionine and from mutant prm 1 were studied. The undermethylated ribosomes had been labeled by addition in vitro or in vivo of radioactive methyl groups from S-adenosylmethionine or from methionine. The following compounds were identified : N alpha-mono-, di- and trimethylalanines, N epsilon-mono-, di- and trimethyllysines, methylamine and N alpha-trimethylalanyllysine. Except for the latter compound and N-alpha-dimethylalanine, all other derivatives had been previously identified in the literature. It is shown that the dipeptide had been in the past mistaken for N epsilon-monomethyllysine, and arises through incomplete hydrolysis in 24 hrs of the N-terminal peptide bond of protein L11. The results of the present study are discussed in the light of previous work on ribosomal protein methylation by the authors and other workers in the field. 相似文献
80.
J Caroff E Girin D Alix C Cann-Moisan J Sizun L Barthelemy 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1992,314(10):451-454
The study of 33 cerebrospinal fluids of infants victims of sudden death shows a very significant increase of the metabolites of dopamine and serotonin. These determinations, compared to a control group, indicate a failure, concerning these two neurotransmitters, which could induce a cardiorespiratory seizure. This failure has likely a multifactorial origin. 相似文献