A 32-kD GTP-binding protein associated with the CD4-p56lck and CD8-p56lck T cell receptor complexes

The guanosine triphosphate (GTP)-binding proteins include signal-transducing heterotrimeric G proteins (for example, Gs, Gi), smaller GTP-binding proteins that function in protein sorting, and the oncogenic protein p21ras. The T cell receptor complexes CD4-p56lck and CD8-p56lck were found to include a 32- to 33-kilodalton phosphoprotein (p32) that was recognized by an antiserum to a consensus GTP-binding region in G proteins. Immunoprecipitated CD4 and CD8 complexes bound GTP and hydrolyzed it to guanosine diphosphate (GDP). The p32 protein was covalently linked to [alpha-32P]GTP by ultraviolet photoaffinity labeling. These results demonstrate an interaction between T cell receptor complexes and an intracellular GTP-binding protein.     

PHOSPHATE INCORPORATION IN DESHEATHED NERVES: EFFECTS OF POTASSIUM AND CALCIUM IONS

In the presence of Ringer's solution containing a high concentration of potassium ions, the incorporation of P(32)-orthophosphate into adenosine triphosphate and other organophosphates of the desheathed sciatic nerve of the bullfrog was inhibited by more than 75 percent. In calcium-free Ringer's solution containing ethylenediaminetetraacetic acid, the inhibition was about 30 percent. Both solutions depolarized the nerves, and the depolarization probably interfered with the mechanisms of phosphate transfer rather than directly with phosphorylation. The inhibition may have been a consequence of the decreased adsorption of phosphates which occurs at the excitable surface during depolarization.     

Phosphorylation of dipteran chromosomes and rat liver nuclei

Side-chain modifications of the nucleoproteins are believed to be involved in the control of gene function. Rat liver nuclei and chromatin incubated in adenosine triphosphate labeled in the gamma position with phosphorus-32 demonstrated rapid phosphorylation in vitro of the nuclear proteins. Dipteran salivary glands incubated in either labeled adenosine triphosphate or ortho-phosphate labeled with phosphorus-32 showed that there is phosphorylation of chromosomal protein. The phosphorus is associated in protein from both liver and salivary gland nuclei predominantly with phosphoserine.     

Assembly of clathrin-coated pits onto purified plasma membranes

During receptor-mediated endocytosis, coated pits invaginate to form coated vesicles, clathrin and associated proteins dissociate from the vesicle membrane, and these proteins form new coated pits at the cell surface. As a means of elucidating molecular mechanisms that govern the function of coated pits, the assembly phase of this cycle was reconstituted by incubating purified membranes that were treated to remove endogenous coated pits with cytoplasm extracted from cultured cells. The in vitro assembly of coated pits on these membranes satisfactorily mimics many features of coated pit formation in the intact cell. These studies indicate that: the membranes contain a limited number of coated pit assembly sites that bind clathrin with high affinity; the half-time for assembly is 5 minutes both at 4 degrees C and 37 degrees C; during assembly, proteins with molecular sizes of 180, 110, and 36 kilodaltons are recruited to the plasma membrane; and assembly is not dependent on adenosine triphosphate, but this nucleotide triggers a temperature-dependent loss of coated pits that are assembled in the absence of adenosine triphosphate.     

Renal adenyl cyclase: anatomically separate sites for parathyroid hormone and vasopressin

Adenyl cyclase from plasma membrane fractions of rat renal cortex or medulla was assayed by measuring conversion of adenosine triphosphate labeled at the alpha-phosphate with (32)P to cyclic 3',5'-adenosine monophosphate labeled with 32P. Parathyroid hormone activated the enzyme primarily in cortex; vasopressin acted primarily in medulla. These experiments support the conclusion that cyclic adenosine monophosphate mediates the action of parathyroid hormone on the kidney and show that parathyroid hormone and vasopressin stimulate adenyl cyclase at anatomically separable areas within the kidney.     

杨树苗木蛋白质与内源激素的动态变化研究

[目的]研究杨树苗木蛋白质与内源激素的动态变化。[方法]以1年生杨树无性系797杨（P．deltoides×Peuramericana）苗木为材料，研究其叶片和苗木主干皮层中总蛋白质含量的年动态变化。并用酶联免疫法测定同时期叶片和苗木主干皮层中内源激素的含量变化，分析内源激素与蛋白质含量变化的相关性。[结果]1年生杨树苗木叶片和主干皮层中总蛋白质含量变化趋势相反。春季展叶期间叶片总蛋白质含量较高，皮层含量较低；进入秋冬季节，叶片含量降低，皮层开始逐渐积累蛋白质。内源激素季节性变化起伏波动较大，与蛋白质变化密切相关，并间接地调控杨树营养贮藏蛋白质的降解与合成。[结论]探索植物激素在杨树氮素代谢过程中的调控作用，为杨树丰产栽培提供科学依据。     

3H]adenosine triphosphate: release during stimulation of enteric nerves

The isolated taenia coli of the guinea pig takes up tritiated adenosine, adenosine monophosphate, adenosine diphosphate, and adenosine triphosphate, in preference to tritiated inosine and adenine. After uptake, [(3)H]adenosine is converted and retained primarily as [(3)H]adenosine triphosphate. Tritium is released from taenia coli treated with [(3)H]adenosine upon activation of the nonadrenergic inhibitory nerves. These results are consistent with the previous evidence that adenosine triphosphate may be the transmitter from the nerves.     

Phosphoryl transfer and calcium ion occlusion in the calcium pump

A tight coupling between adenosine triphosphate (ATP) hydrolysis and vectorial ion transport has to be maintained by ATP-consuming ion pumps. We report two crystal structures of Ca2+-bound sarco(endo)plasmic reticulum Ca2+-adenosine triphosphatase (SERCA) at 2.6 and 2.9 angstrom resolution in complex with (i) a nonhydrolyzable ATP analog [adenosine (beta-gamma methylene)-triphosphate] and (ii) adenosine diphosphate plus aluminum fluoride. SERCA reacts with ATP by an associative mechanism mediated by two Mg2+ ions to form an aspartyl-phosphorylated intermediate state (Ca2-E1 approximately P). The conformational changes that accompany the reaction with ATP pull the transmembrane helices 1 and 2 and close a cytosolic entrance for Ca2+, thereby preventing backflow before Ca2+ is released on the other side of the membrane.     

Interaction of Hsp 70 with newly synthesized proteins: implications for protein folding and assembly

The 70-kilodalton family of heat shock proteins (Hsp 70) has been implicated in posttranslational protein assembly and translocation. Binding of cytosolic forms of Hsp 70 (Hsp 72,73) with nascent proteins in the normal cell was investigated and found to be transient and adenosine triphosphate (ATP)-dependent. Interaction of Hsp 72,73 with newly synthesized proteins appeared to occur cotranslationally, because nascent polypeptides released prematurely from polysomes in vivo can be isolated in a complex with Hsp 72,73. Moreover, isolation of polysomes from short-term [35S]Met-labeled cells (pulsed) revealed that Hsp 72,73 associated with nascent polypeptide chains. In cells experiencing stress, newly synthesized proteins coimmunoprecipitated with Hsp 72,73; however, in contrast to normal cells, interaction with Hsp 72,73 was not transient. A model consistent with these data suggests that under normal growth conditions, cytosolic Hsp 72,73 interact transiently with nascent polypeptides to facilitate proper folding, and that metabolic stress interferes with these events.     

Tritiated digoxin binding to (Na+ + K+)-activated adenosine triphosphatase: possible allosteric site

Tritiated H(3)-digoxin specifically binds to a cardiac (Na(+) + K(+))-activated adenosine triphosphatase. In the presence of adenosine triphosphate and other nucleoside di- and triphosphates, binding is stimulated by sodium ion, the apparent rate constant being similar to that reported for phosphorus-32 incorporation from adenosine triphosphate and for the adenosine triphosphatase activity. In the presence of magnesium, manganese, inorganic phosphate, or other ions, sodium ion inhibits binding. The data support an allosteric type of sodium-potassium ion pump.     

Quinacrine: mechanisms of antimalarial action

Two new interesting modes of action of quinacrine have been discovered. The first concerns a dose-related inhibition of uptake of [8-(3)H] adenosine into host cells of parasitized blood. Second, the drug inhibits the incorporation of tritiated adenosine triphosphate primarily into RNA but also into DNA of the erythrocyte-free malarial parasite Plasmodium berghei.     

黄条金刚竹叶提取物抑菌活性研究

[目的]研究黄条金刚竹叶提取物的抑菌活性。[方法]以黄条金刚竹叶的水提取物、石油醚提取物、乙酸乙酯提取物和正丁醇提取物分别对大肠杆菌(Escherichia coli)、枯草芽孢杆菌(Bacillus subtilis)、金黄色葡萄球菌(Staphylococcus aureus)、啤酒酵母(Saccharomycescarlsbergensis)、黄曲霉(Aspergillus.flavus)、产黄青霉(Penicillium chrysogenum)6种菌进行抑菌活性研究。[结果]试验表明,黄条金刚竹叶的正丁醇提取物和乙酸乙酯提取物对3种细菌都有一定的抑菌效果,水提取物和石油醚提取物对细菌的抑菌效果不明显;正丁醇提取物对3种真菌都有一定的抑菌效果。[结论]研究可为竹叶提取物抑菌性的应用提供理论依据。     

微波条件下淀粉与苯乙烯接枝共聚研究

[目的]利用微波技术对淀粉-苯乙烯接枝共聚物的合成进行研究。[方法]以焦磷酸锰络阴离子为引发剂,以十二烷基硫酸钠为乳化剂,采用正交试验筛选通过微波加热,玉米淀粉与苯乙烯接枝共聚反应的最佳条件。[结果]淀粉与苯乙烯接枝共聚反应的最佳组合条件为：苯乙烯用量20ml,焦磷酸锰络阴离子浓度9mmol/L,反应时间14min（30s＋30s）。[结论]该研究确定了淀粉-苯乙烯接枝共聚物合成的最佳工艺条件。     

Mitochondrial polyriboadenylate polymerase: relative lack of activity in hepatomas

An enzyme that polymerizes adenylate residues from adenosine triphosphate was prepared from rat liver mitochondria and compared to similar preparations from the mitochondria of three hepatomas. Enzyme activity in the hepatomas was only 1 to 2 percent of that in normal liver.     

生防菌菌株A的摇瓶培养条件及发酵工艺

[目的]优化生防菌菌株A的培养条件与液体发酵工艺。[方法]采用均匀试验设计方法、回归分析方法和分批补料发酵工艺,研究生防菌菌株A的培养条件与液体发酵工艺的优化。[结果]结果表明,适合菌株A摇瓶培养的最佳条件为：培养温度35℃,摇瓶装量12％,接种量3．0％,初始pH值7．2。20L发酵罐分批补料发酵参数为：种子培养基为YDC培养基,培养时间24h,接种量3．0％;发酵培养基：葡萄糖1．0％,酵母膏1．0％,CaCO3 1．0％,pH值7．2;流加培养基：葡萄糖1．5％,酵母膏0．5％,制成混合液一起流加,发酵8h开始流加;发酵周期（34±2）h,在以上发酵条件下,发酵液芽孢浓度达（3．410±0．151）×10^9cfu／ml。[结论]该试验条件下所获得发酵液芽孢数浓度较高,可用于进一步制备生防菌剂。     

Human diabetes associated with a mutation in the tyrosine kinase domain of the insulin receptor

Insulin receptor complementary DNA has been cloned from an insulin-resistant individual whose receptors have impaired tyrosine protein kinase activity. One of this individual's alleles has a mutation in which valine is substituted for Gly996, the third glycine in the conserved Gly-X-Gly-X-X-Gly motif in the putative binding site fo adenosine triphosphate. Expression of the mutant receptor by transfection into Chinese hamster ovary cells confirmed that the mutation impairs tyrosine kinase activity.     

南五味子不同溶剂提取物的抑菌活性研究

[目的]研究南五味子的乙醇提取物和水提取物的抑菌活性。[方法]分离南五味子提取物中的乙醇相物质和水相物质,用牛津杯法测定其对常见的致病菌和酵母菌的抑菌活性,用平板涂布法测定最低抑菌浓度(MIC)和最低杀菌浓度(MBC)。[结果]南五味子的醇相和水相物质对革兰氏阳性菌(G+)和革兰氏阴性菌(G-)均有明显的抑菌活性,对G+的抑菌活性均强于对G-的抑菌活性;醇相的抑菌活性优于水相的抑菌活性;对酵母菌的抑菌活性均不明显;醇相和水相的抑菌活性顺序均依次为:金黄色葡萄球菌>枯草芽孢杆菌>大肠杆菌>沙门氏菌>酵母菌。[结论]南五味子的乙醇提取物和水提取物均有一定的抑菌活性,值得进一步开发利用。     

Leaf closure in the venus flytrap: an Acid growth response

The rapid closure of leaves in the Venus flytrap (Dionaea muscipula) involves irreversible cell enlargement, which can be initiated by acidifying the cell walls to pH 4.50 and below. Leaves infiltrated with neutral buffers that keep the pH above 4.50 to 4.75 will not close in response to stimulation of their trigger hairs even though the action potentials that ordinarily cause closure are produced. During the 1 to 3 seconds required for closure about 29 percent of the cellular adenosine triphosphate is lost. It is likely that this adenosine triphosphate is used in very rapid transport of hydrogen ions from the motor cells and that the movement is due to a mechanism of "acid growth."