Effect of Putrescine on Low-Temperature Acclimation in <i>Chlamydomonas reinhardtii</i>

Putrescine is reported to be necessary for cold acclimation under low-temperature stress. In this study, the effect of low-temperature on some physiological and biochemical parameters has been investigated using the green algae Chlamydomonas reinhardtii. The lipid peroxidation rate, amount of Rubisco protein, activities of antioxidant enzymes and gene expression of polyamine biosynthesis (odc2, and spd1), heat shock proteins (hsp70c, hsp90a, and hsp90c), and PSII repair mechanisms (psba, rep27, and tba1) were determined to understand the low-temperature response. Exogenous putrescine application significantly increased Rubisco protein concentration and catalase enzyme activities under low-temperature stress. Moreover, real-time RT-PCR results and gene expression analysis showed that polyamine metabolism induced gene expression at low-temperatures in the first 24 h. In the same way, the gene expression of heat shock proteins (hsp70c, hsp90a, and hsp90c) decreased under low-temperature treatment for 72 h; however, application of putrescine enhanced the gene expression in the first 24 h. The results obtained indicated that molecular response in the first 24 h could be important for cold acclimation. The psba and tba1 expressions were reduced under low-temperatures depending on the exposure time. In contrast, the exogenous putrescine enhanced the expression level of the psba response to low-temperature at 24 and 72 h. The results obtained in this study indicate that putrescine could play a role in the PS II repair mechanisms under low-temperature stress.     

Examination of Changes in Enzyme Activities of Erythrocyte Glucose 6‐Phosphate Dehydrogenase and 6‐Phosphogluconate Dehydrogenase in Rats Given Naringenin and Lead Acetate

In our study, controlled experimental groups were performed by giving substances Lead acetate, Naringenin and Naringenin + Lead acetate to rats in vivo conditions Changes in the glucose 6‐phosphate dehydrogenase (G6PD) and 6‐phosphogluconate dehydrogenase (6PGD) enzyme activities in erythrocytes of rats in these groups were compared to the Control group. An inhibition significant degree for G6PD enzyme activity was observed in all groups when compared to the Control group (p < 0.001). While inhibition significant degree for 6PGD enzyme activity was observed in Lead acetate groups (p < 0.001), no significant effect was observed in the Naringenin and Naringenin + Lead acetate groups (p > 0.05). In addition, lead levels in the groups of rats were determined using an inductively coupled plasma mass spectrometer (ICP‐MS) device. As a result of measurements by the ICP‐MS device, lead levels were found as an average of 42.9 ± 2.51, 36.71 ± 1.13, 172.16 ± 9.63, and 95.07 ± 5.87 ppm in the Control, Naringenin, Lead acetate and Naringenin + Lead acetate groups, respectively. Our results were shown that Naringenin has protective effects on the Lead acetate induced oxidative stress erythrocytes in rat.     

Receptor-mediated reversible translocation of the G protein betagamma complex from the plasma membrane to the Golgi complex

Heterotrimeric G proteins have been thought to function on the plasma membrane after activation by transmembrane receptors. Here we show that, after activation by receptors, the G protein betagamma complex selectively translocates to the Golgi. Receptor inactivation results in Gbetagamma translocating back to the plasma membrane. Both translocation processes occur rapidly within seconds. The efficiency of translocation is influenced by the type of gamma subunit present in the G protein. Distinctly different receptor types are capable of inducing the translocation. Receptor-mediated translocation of Gbetagamma can spatially segregate G protein signaling activity.     

Cloning,purification and characterization of an alkali-stable endoxylanase from thermophilic <Emphasis Type="Italic">Geobacillus</Emphasis> sp. 71

The gene encoding a xylanase from Geobacillus sp. 71 was isolated, cloned, and sequenced. Purification of the Geobacillus sp 7.1 xylanase, XyzGeo71, following overexpression in E. coli produced an enzyme of 47 kDa with an optimum temperature of 75°C. The optimum pH of the enzyme is 8.0, but it is active over a broad pH range. This protein showed the highest sequence identity (93%) with the xylanase from Geobacillus thermodenitrificans NG80-2. XyzGeo71 contains a catalytic domain that belongs to the glycoside hydrolase family 10 (GH10). XyzGeo71 exhibited good pH stability, remaining stable after treatment with buffers ranging from pH 7.0 to 11.0 for 6 h. Its activity was partially inhibited by Al³⁺ and Cu²⁺ but strongly inhibited by Hg²⁺. The enzyme follows Michaelis–Menten kinetics, with K_m and V_max values of 0.425 mg xylan/ml and 500 μmol/min.mg, respectively. The enzyme was free from cellulase activity and degraded xylan in an endo fashion. The action of the enzyme on oat spelt xylan produced xylobiose and xylotetrose.     

Purification and Characterization of Carbonic Anhydrase from Ağrı Balık Lake Trout Gill (Salmo trutta labrax) and Effects of Sulfonamides on Enzyme Activity

Carbonic anhydrase (CA) was purified from A?r? Bal?k Lake trout gill (fCA) by affinity chromatography on a sepharose 4B‐tyrosine‐sulfanilamide column. The fCA enzyme was purified with about a 303.9 purification factor, a specific activity 4130.4 EU (mg‐protein)^–1, and a yield of 79.3 by using sepharose‐4B‐l tyrosine‐sulfanilamide affinity gel chromatography. The molecular weight determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) was found to be about 29.9 kDa. The kinetic parameters, K_M and V_max were determined for the 4‐nitrophenyl acetate hydrolysis reaction. Some sulfonamides were tested as inhibitors against the purified CA enzymes. The K_i constants for mafenide ( 1 ), p‐toluenesulfonamide ( 2 ), 2‐bromo‐benzene sulfonamide ( 3 ), 4‐chlorobenzene sulfonamide ( 4 ), 4‐amino‐6‐chloro‐1–3 benzenedisulfonamide ( 5 ), sulfamethazine ( 6 ), sulfaguanidine ( 7 ), sulfadiazine ( 8 ), and acetozazolamide ( 9 ) were in the range of 7.5–108.75 μM.     

Mutational analysis of Turnip crinkle virus movement protein p8

Turnip crinkle virus encodes two proteins, p8 and p9, that are both required for cell-to-cell movement. The p8 movement protein has been demonstrated to bind RNA in a cooperative manner, although, similar to many other plant virus movement proteins, it contains no canonical RNA binding domain(s). However, three positively charged regions of p8 may potentially form ionic interactions with the RNA backbone. To identify functional regions of p8, a series of alanine and deletion scanning mutations were produced. The effects of these mutations were analysed using both in vitro RNA binding assays and in vivo infections of susceptible (Di-3) and resistant (Di-17) Arabidopsis thaliana plants. Several mutants that have reduced RNA binding ability were also demonstrated to be movement deficient and replication competent. Based on these results, there appear to be two regions, located between amino acids 18 and 31, and 50 and 72, that are required for RNA binding. Furthermore, additional regions (amino acids 12–15, and 34–37) appear to play a role in vivo unrelated to in vitro RNA binding activity.     

G protein betagamma11 complex translocation is induced by Gi, Gq and Gs coupling receptors and is regulated by the alpha subunit type

G protein activation by Gi/Go coupling M2 muscarinic receptors, Gq coupling M3 receptors and Gs coupling beta2 adrenergic receptors causes rapid reversible translocation of the G protein gamma11 subunit from the plasma membrane to the Golgi complex. Co-translocation of the beta1 subunit suggests that gamma11 translocates as a betagamma complex. Pertussis toxin ADP ribosylation of the alphai subunit type or substitution of the C terminal domain of alphao with the corresponding region of alphas inhibits gamma11 translocation demonstrating that alpha subunit interaction with a receptor and its activation are requirements for the translocation. The rate of gamma11 translocation is sensitive to the rate of activation of the G protein alpha subunit. alpha subunit types that show high receptor activated rates of guanine nucleotide exchange in vitro support high rates of gamma11 translocation compared to alpha subunit types that have a relatively lower rate of guanine nucleotide exchange. The results suggest that the receptor induced translocation of gamma11 is controlled by the rate of cycling of the G protein through active and inactive forms. They also demonstrate that imaging of gamma11 translocation can be used as a non-invasive tool to measure the relative activities of wild type or mutant receptor and alpha subunit types in a live cell.