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141.
Wouters MA Lau KK Hogg PJ 《BioEssays : news and reviews in molecular, cellular and developmental biology》2004,26(1):73-79
Cross-strand disulphides (CSDs) are unusual bonds that link adjacent strands in the same beta-sheet. Their peculiarity relates to the high potential energy stored in these bonds, both as torsional energy in the highly strained disulphide linkage and as deformation energy stored in the sheet itself. CSDs are relatively rare in protein structures but are conspicuous by their presence in proteins that are involved in cell entry. The finding that entry of botulinum neurotoxin and HIV into mammalian cells involves cleavage of CSDs suggests that the activity of other cell entry proteins may likewise involve cleavage of these bonds. We examine emerging evidence of the involvement of these unusual disulphides in cell entry events. 相似文献
142.
TM?Matthews RK?Duncan M?Zidanic TH?Michael PA?FuchsEmail author 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2005,191(6):491-503
In the inner ear of birds, as in mammals, reptiles and amphibians, acetylcholine released from efferent neurons inhibits hair cells via activation of an apamin-sensitive, calcium-dependent potassium current. The particular potassium channel involved in avian hair cell inhibition is unknown. In this study, we cloned a small-conductance, calcium-sensitive potassium channel (gSK2) from a chicken cochlear library. Using RT-PCR, we demonstrated the presence of gSK2 mRNA in cochlear hair cells. Electrophysiological studies on transfected HEK293 cells showed that gSK2 channels have a conductance of approximately 16 pS and a half-maximal calcium activation concentration of 0.74±0.17 M. The expressed channels were blocked by apamin (IC50=73.3±5.0 pM) and d-tubocurarine (IC50=7.6±1.0 M), but were insensitive to charybdotoxin. These characteristics are consistent with those reported for acetylcholine-induced potassium currents of isolated chicken hair cells, suggesting that gSK2 is involved in efferent inhibition of chicken inner ear. These findings imply that the molecular mechanisms of inhibition are conserved in hair cells of all vertebrates. 相似文献
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Wouters MA Rigoutsos I Chu CK Feng LL Sparrow DB Dunwoodie SL 《Protein science : a publication of the Protein Society》2005,14(4):1091-1103
EGF domains are extracellular protein modules cross-linked by three intradomain disulfides. Past studies suggest the existence of two types of EGF domain with three-disulfides, human EGF-like (hEGF) domains and complement C1r-like (cEGF) domains, but to date no functional information has been related to the two different types, and they are not differentiated in sequence or structure databases. We have developed new sequence patterns based on the different C-termini to search specifically for the two types of EGF domains in sequence databases. The exhibited sensitivity and specificity of the new pattern-based method represents a significant advancement over the currently available sequence detection techniques. We re-annotated EGF sequences in the latest release of Swiss-Prot looking for functional relationships that might correlate with EGF type. We show that important post-translational modifications of three-disulfide EGFs, including unusual forms of glycosylation and post-translational proteolytic processing, are dependent on EGF subtype. For example, EGF domains that are shed from the cell surface and mediate intercellular signaling are all hEGFs, as are all human EGF receptor family ligands. Additional experimental data suggest that functional specialization has accompanied subtype divergence. Based on our structural analysis of EGF domains with three-disulfide bonds and comparison to laminin and integrin-like EGF domains with an additional inter-domain disulfide, we propose that these hEGF and cEGF domains may have arisen from a four-disulfide ancestor by selective loss of different cysteine residues. 相似文献
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E Kohen J G Hirschberg C Kohen A Wouters A Pearson J M Salmon B Thorell 《Biochimica et biophysica acta》1975,396(1):149-154
Starting from a previously described prototype microspectrofluorometer a more versatile apparatus has been developed with rapid optional operation on a topographic mode for the simultaneous multisite evaluation of NAD(P) reduction-reoxidation transients or on a spectral mode for the analysis of natural and exogenous fluorochromes, in single living cells. On the topographic mode, adetailed kinetic analysis of NAD or NAD P-linked dehydrogenases can be made from 50-100 cell points imultaneously via automatic recording of topographic scans upt to 16 times a second, in correlation with microelectrophoretic intracellular inuection of metabolites (e.g. nearly immediate response to glucose 6-phosphate, 20-25 s delay for 6-phosphogluconate). Rapid shifts from topographic to spectral operation make possible the detection of a change in fluorescence intensity at a specific intracellular site and the immediate verification of its nature (NAD(P)H or exogenous fluorochrome) by spectral observations. 相似文献
150.
Abandoning ineffective medical practices and mitigating the risks of untested practices are important for improving patient health and containing healthcare costs. Historically, this process has relied on the evidence base, societal values, cultural tensions, and political sway, but not necessarily in that order. We propose a conceptual framework to guide and prioritize this process, shifting emphasis toward the principles of evidence-based medicine, acknowledging that evidence may still be misinterpreted or distorted by recalcitrant proponents of entrenched practices and other biases. 相似文献