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81.
82.
Tapas K. Nandi Hridoy R. Bairagya Bishnu P. Mukhopadhyay K. Sekar Dipankar Sukul Asim K. Bera 《Journal of biosciences》2009,34(1):27-34
The role of invariant water molecules in the activity of plant cysteine protease is ubiquitous in nature. On analysing the
11 different Protein DataBank (PDB) structures of plant thiol proteases, the two invariant water molecules W1 and W2 (W220
and W222 in the template 1PPN structure) were observed to form H-bonds with the Ob atom of Asn 175. Extensive energy minimization and molecular dynamics simulation studies up to 2 ns on all the PDB and solvated
structures clearly revealed the involvement of the H-bonding association of the two water molecules in fixing the orientation
of the asparagine residue of the catalytic triad. From this study, it is suggested that H-bonding of the water molecule at
the W1 invariant site better stabilizes the Asn residue at the active site of the catalytic triad. 相似文献
83.
84.
J K Skipper F I Davidson D F Smith T H Hamilton 《The Journal of biological chemistry》1985,260(9):5399-5405
Conditions are defined which permit analysis of estrogen receptors from the mammalian uterus by polyacrylamide gel electrophoresis, thereby solving a longstanding problem encountered in previous attempts at such analysis, namely the failure of a large portion of the receptor population to enter such gels. A paramount requirement for entry of the estrogen-receptor complex into polyacrylamide gels is its maintenance in an untransformed state which does not form aggregates that are excluded from these gels. Of the multiple estrogen-binding proteins separated, only one (relative mobility of 0.5-0.6) possessed the definitive characteristics of the classical estrogen receptor. The inclusion of molybdate in extraction buffers selectively enhanced receptor recovery and facilitated its separation. Moreover, the estrogen-receptor complex so resolved is separated from other types of estrogen-binding proteins present in the uterine cytosol. These findings show that the molybdate-stabilized estrogen receptor exists in a single discrete form, but otherwise exhibits multiple forms that are probably artifactual. Electrophoresis in discontinuous buffers, but not in a continuous buffer system, promoted aggregate formation. This finding has implications concerning the subunit structure of the untransformed receptor. 相似文献
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86.
Mingyue Wang Pranab K Mukherjee Jyotsna Chandra Ali Abdul Lattif Thomas S McCormick Mahmoud A Ghannoum 《BMC microbiology》2008,8(1):31
Background
We have previously shown that supernatant from Candida albicans (CA) culture contains a Secretory Interleukin (IL)-12 Inhibitory Factor (CA-SIIF), which inhibits IL-12 production by human monocytes. However, the effect of CA-SIIF on secretion of other cytokines by monocytes is unknown, and detailed characterization of this factor has not been performed. 相似文献87.
Dana M. Bergstrom George R. Stewart Patricia M. Selkirk Susanne Schmidt 《Oecologia》2002,130(2):309-314
'15N signatures of fossil peat were used to interpret past ecosystem processes on tectonically active subantarctic Macquarie Island. By comparing past vegetation reconstructed from the fossil record with present-day vegetation analogues, our evidence strongly suggests that changes in the '15N signatures of fossil peat at this location reflect mainly past changes in the proportion of plant nitrogen derived from animal sources. Associated with uplift above sea level over the past 8,500 years, fossil records in two peat deposits on the island chronicle a change from coastal vegetation with fur and elephant seal disturbance to the existing inland herbfield. Coupled with this change are synchronous changes in the '15N signatures of peat layers. At two sites 15N-enriched peat '15N signatures of up to +17 were associated with a high abundance of pollen of the nitrophile Callitriche antarctica (Callitrichaceae). At one site fossil seal hair was also associated with enriched peat '15N. Less 15N enriched '15N signatures (e.g. -1.9 to +3.9) were measured in peat layers which lacked animal associated C. antarctica and Acaena spp. Interpretation of a third peat profile indicates continual occupation of a ridge site by burrowing petrels for most of the Holocene. We suggest that 15N signatures of fossil peat remained relatively stable with time once deposited, providing a significant new tool for interpreting the palaeoecology. 相似文献
88.
Enhanced fluorescence of the ATP analogue 2',3'-O-(2,4,6-trinitrocyclohexyldienylidine)adenosine 5'-triphosphate (TNP-ATP), bound to the Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum, is closely related to phosphoenzyme levels (Bishop, J. E., Johnson, J. D., and Berman, M. C. (1984) J. Biol. Chem. 259, 15163-15171) and has an emission maximum consistent with decreased polarity of the TNP-ATP-binding site. The phosphoenzyme conformation responsible for increased nucleotide-binding site hydrophobicity has been studied by redistribution of phosphoenzyme intermediates following specific thiol group modification. N-Ethylmaleimide, in the presence of 50 microM Ca2+, 1 mM adenyl-5'-yl imidodiphosphate, pH 7.0, at 25 degrees C for 30 min, selectively modified the SH group essential for phosphoenzyme decomposition, which resulted in decreased ATPase activity, Ca2+ uptake, and a decrease in ATP-induced TNP-ATP fluorescence. Phosphorylated (Ca2+, Mg2+)-ATPase levels from [gamma-32P] ATP remained relatively unaffected (3.1 nmol/mg), but the ADP-insensitive fraction decreased from 56 to 15%. Phosphoenzyme levels from 32Pi were also decreased to the same extent as turnover, with equivalent loss of Pi-induced TNP-ATP fluorescence. The E1 to E2 transition, as monitored by the change in intrinsic tryptophan fluorescence, was unaffected. Modification of thiol groups of unknown function did not modify turnover-induced TNP-ATP fluorescence. It is concluded that the ADP-insensitive phosphoenzyme, E2-P, is responsible for enhanced TNP-ATP fluorescence. This suggests that the conformational transition, 2Ca2+outE1 approximately P----2Ca2+inE2-P, is associated with altered properties of the noncatalytic, or regulatory, nucleotide-binding site. 相似文献
89.
90.