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1.
The direct binding of porcine pancreatic phospholipase A2 and its zymogen to 1,2-bis(heptanylcarbamoyl)-rac-glycerol 3-sulfate was studied by optical detection of triplet-state magnetic resonance spectroscopy in zero applied magnetic field. The zero-field splittings of the single Trp3 residue undergo significant changes upon binding of phospholipase A2 to lipid. Shifts in zero-field splittings, characterized mainly by a reduction of the E parameter from 1.215 to 1.144 GHz, point to large changes in the Trp3 local environment which accompany the complexing of phospholipase A2 with lipid. This may be attributed to Stark effects caused by the binding of a charged group near Trp3 in the enzyme-lipid complex. The cofactor, Ca2+, which is strongly bound to the enzyme active site, has an influence on the bonding, as reflected by smaller zero-field splitting shifts. A relatively small change in the Trp environment was observed for the interaction of the zymogen with lipid. 相似文献
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Changes in Targeting Efficiencies of Proteins to Plant Microbodies Caused by Amino Acid Substitutions in the Carboxy-terminal Tripeptide 总被引:7,自引:0,他引:7
Hayashi Makoto; Aoki Masahiro; Kondo Maki; Nishimura Mikio 《Plant & cell physiology》1997,38(6):759-768
It has been demonstrated that the carboxyl terminus of microbodyenzymes functions as a targeting signal to microbodies in higherplants. We have examined an ability of 24 carboxy-terminal aminoacid sequences to facilitate the transport of a cytosolic passengerprotein, ß-glucuroni-dase, into microbodies in greencotyledonary cells of trans-genic Arabidopsis. Immunoelectronmicroscopic analysis revealed that carboxy-terminal tripeptidesequences of the form [C/A/S/P]-[K/R]-[I/L/M] function as amicrobody-targeting signal, although tripeptides with prolineat the first amino acid position and isoleucine at the carboxylterminus show weak targeting efficiencies. All known micro-bodyenzymes that are synthesized in a form similar in size to themature molecule, except catalase, contain one of these tripeptidesequences at their carboxyl terminus. (Received April 14, 1997; Accepted April 8, 1997) 相似文献
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T Nishida 《Folia primatologica; international journal of primatology》1988,50(1-2):109-123
Grooming between female chimpanzees and their offspring was studied in the Mahale Mountains, Tanzania. Infants under 2 years of age rarely groomed their mothers, and mostly groomed accessible parts of their mother's bodies, if they did so. Most older adolescents reciprocated grooming with their mothers almost equally. Daughters appeared to mature socially earlier than sons, judging from the earlier ages at which a female infant began to groom her mother, groom mutually with her, and groom others. Weaning infants groomed their mothers more when they were in oestrus than when they were not. Development of the use of grooming as a means of social manoeuvring is discussed. 相似文献
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Since deaths of waterfowls have frequently been observed in Lake Kahoku near Kanazawa city, Japan, we attempted an ecological study on Clostridium botulinum type C in four other lakes as well as Lake Kahoku. One hundred and twenty-nine (56%) of 230 soil samples collected gave rise to lethal toxicity in mice with the characteristic “wasp-waist” symptom. All of the 51 samples arbitrarily selected were neutralized by C. botulinum type C antitoxic serum. A further seasonal study throughout the year at a given shore area of Lake Kahoku disclosed that nearly all samples gave rise to toxicity due to C. botulinum type C during the autumn season when the most waterfowls congregate. Toxigenic strains of C. botulinum type C were isolated together with nontoxigenic strains that were culturally and biochemically similar to the toxigenic strains. Both the toxigenic and nontoxigenic strains were equally agglutinable by an antiserum prepared against one of the nontoxigenic strains. Further extensive studies on the specificity of the agglutination method for identification were performed with 112 strains of 46 clostridial species. None of the strains used except some strains of C. novyi type A and a strain of C. botulinum type D was agglutinable. Based on the findings for cultural, biochemical, and agglutinable properties, the nontoxigenic strains were identified as C. botulinum type C. Also, C. novyi type A isolates showing colonies covered with a small pearly layer zone but surrounded by an aberrantly wide lecithinase zone are discussed. 相似文献
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Teresa K. Aman Bruce A. Maki Thomas J. Ruffino Eileen M. Kasperek Gabriela K. Popescu 《The Journal of biological chemistry》2014,289(27):18805-18817
Protein kinase A (PKA) enhances synaptic plasticity in the central nervous system by increasing NMDA receptor current amplitude and Ca2+ flux in an isoform-dependent yet poorly understood manner. PKA phosphorylates multiple residues on GluN1, GluN2A, and GluN2B subunits in vivo, but the functional significance of this multiplicity is unknown. We examined gating and permeation properties of recombinant NMDA receptor isoforms and of receptors with altered C-terminal domain (CTDs) prior to and after pharmacological inhibition of PKA. We found that PKA inhibition decreased GluN1/GluN2B but not GluN1/GluN2A gating; this effect was due to slower rates for receptor activation and resensitization and was mediated exclusively by the GluN2B CTD. In contrast, PKA inhibition reduced NMDA receptor-relative Ca2+ permeability (PCa/PNa) regardless of the GluN2 isoform and required the GluN1 CTD; this effect was due primarily to decreased unitary Ca2+ conductance, because neither Na+ conductance nor Ca2+-dependent block was altered substantially. Finally, we show that both the gating and permeation effects can be reproduced by changing the phosphorylation state of a single residue: GluN2B Ser-1166 and GluN1 Ser-897, respectively. We conclude that PKA effects on NMDA receptor gating and Ca2+ permeability rely on distinct phosphorylation sites located on the CTD of GluN2B and GluN1 subunits. This separate control of NMDA receptor properties by PKA may account for the specific effects of PKA on plasticity during synaptic development and may lead to drugs targeted to alter NMDA receptor gating or Ca2+ permeability. 相似文献
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