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Ca2+-transporting adenosine triphosphatase (ATPase) of sarcoplasmic reticulum couples ATP hydrolysis with ion transport. Phosphorylation
of the cytosolic region of the calcium-bound conformation (E1) of the protein leads to drastic conformational rearrangements
of the transmembrane helices and the release of Ca2+. The resulting calcium-free conformation (E2) is less stable than the E1 form. The changes in van der Waals interactions
and interhelical hydrogen bonding in the E1 and E2 conformations were compared. Conformational changes in the transmembrane
region concomitant with the release of Ca2+ mainly affect the number of interhelical hydrogen bonds, which is reduced to half of that in E1 form, whereas the number
of interhelical atomic pairwise contacts reflecting van der Waals interactions experience little change. The interhelical
hydrogen bonds in Ca2+-transporting ATPase can be divided into two groups according to their roles: those that play a structural stabilizing role
and those that are important for the correct geometry of the Ca2+ binding site. Interhelical hydrogen bonds in the transmembrane regions play important roles for the stability and specificity
of helix-helix interactions in proteins where change of conformation is required for transport of ions or small molecules. 相似文献
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The NOAH/DIAMOD suite uses feedback filtering and self-correcting distance geometry to generate 3D structures from unassigned NOESY spectra. In this study we determined the minimum set of experiments needed to generate a high quality structure bundle. Different combinations of 3D 15N-edited, 13C-edited HSQC-NOESY and 2D homonuclear 1H-1H NOESY spectra of the 77 amino acid protein, myeloid progenitor inhibitory factor-1 (MPIF-1) were used as input for NOAH/DIAMOD calculations. The quality of the assignments of NOESY cross peaks and the accuracy of the automatically generated 3D structures were compared to those obtained with a conventional manual procedure. Combining data from two types of experiments synergistically increased the number of peaks assigned unambiguously in both individual spectra. As a general trend for the accuracy of the structures we observed structural variations in the backbone fold of the final structures of about 2 Å for single spectral data, of 1 Å to 1.5 Å for double spectral data, and of 0.6 Å for triple spectral data sets. The quality of the assignments and 3D structures from the optimal data using all three spectra were similar to those obtained from traditional assignment methods with structural variations within the bundle of 0.6 Å and 1.3 Å for backbone and heavy atoms, respectively. Almost all constraints (97%) of the automatic NOESY cross peak assignments were cross compatible with the structures from the conventional manual assignment procedure, and an even larger proportion (99%) of the manually derived constraints were compatible with the automatically determined 3D structures. The two mean structures determined by both methods differed only by 1.3 Å rmsd for the backbone atoms in the well-defined regions of the protein. Thus NOAD/DIAMOD analysis of spectra from labeled proteins provides a reliable method for high throughput analysis of genomic targets. 相似文献
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Minasian SM Baklavadzhian OG Adamian TsI Sarkisian SG Saakian SG Gevorkian ES 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》1997,83(3):73-78
A modulating character of the amygdala basolateral nuclei effect upon the vestibular sensory system was determined in rabbits [correction of rats]. A mechanism of the descending effect of the amygdaloid complex on the activity of the Deiters nucleus neurons, is discussed. 相似文献
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S S Gambarov A M Khzardzhian N V Adamian A V Shakhsuvarov A A Suzdal'tseva 《Biulleten' eksperimental'no? biologii i meditsiny》1986,101(5):598-600
B-activin blocks the effect of concanavalin A-induced human T-suppressors, without influencing the process of their induction. 相似文献
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Frog sartorius muscles subjected to loading with Na in K-free Ringer solution in the cold were subsequently labelled with 22Na. The uptake of 22Na is not sensitive to ouabain (10(-4) M) while sodium efflux is decreased by oubain. It is concluded that ouabain-sensitive Na-for Na interchange is not present in this condition. Possibly ouabain-sensitive sodium efflux is partly or completely potassium-requiring fraction since some K (approximately 10 microM) is inevitably present in K-free solution. The increase in the rate constant for potassium loss in the presence of ouabain favours this supposition. 相似文献
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