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71.
A change in twist of actin provides the force for the extension of the acrosomal process in limulus sperm: the false-discharge reaction 总被引:1,自引:5,他引:1 下载免费PDF全文
One of the most spectacular motions is the generation of the acrosomal process in the limulus sperm. On contact with the egg, the sperm generates a 60-mum-long process that literally drills its way through the jelly surrounding the egg. This irresversible reaction takes only a few seconds. We suggested earlier that this motion is driven by a change in twist of the actin filaments comprising the acrosomal process. In this paper we analyze the so-called false discharge, a reversible reaction, in which the acrosomal filament bundle extends laterally from the base of the sperm and not anteriorly from the apex. Unlike the true discharge, which is straight, the false discharge is helical. Before extension, the filament bundle is coiled about the base of the sperm. In the coil, the bundle is not smoothly bent but consists of arms (straight segments) and elbows (corners) so that the coil looks like a 14-sided polygon. The extension of the false discharge works as follows: starting at the base of the bundle, the filaments change their twist which concomitantly changes the orientations of the elbows relative to each other; that is, in the coil, the elbows all like in a common plane, but after the change in twist, the plane of each elbow is rotated to be perpendicular to that of its neighbors. This change transforms the bundle from a compact coil into an extended left- handed helix. Because the basal end of the bundle is unconstrained, the extension is lateral. The true discharge works the same way but starts at the apical end of the bundle. The apical end, however, is constrained by its passage through the nuclear canal, which directs the extention anteriorly. Unlike the false discharge, during the true discharge the elbows are melted out, making the reaction irreversible. This study shows that rapid movement can be regenerated by actin without myosin and gives us insight into the molecular mechanism. 相似文献
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Willoughby CA Rosauer KG Hale JJ Budhu RJ Mills SG Chapman KT MacCoss M Malkowitz L Springer MS Gould SL DeMartino JA Siciliano SJ Cascieri MA Carella A Carver G Holmes K Schleif WA Danzeisen R Hazuda D Kessler J Lineberger J Miller M Emini EA 《Bioorganic & medicinal chemistry letters》2003,13(3):427-431
A new class of 4-(aminoheterocycle)piperidine derived 1,3,4 trisubstituted pyrrolidine CCR5 antagonists is reported. Compound 4a is shown to have good binding affinity (1.8 nM) and antiviral activity in PBMC's (IC(95)=50 nM). Compound 4a also has improved PK properties relative to 1. 相似文献
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Dooseop Kim Liping Wang Charles G. Caldwell Ping Chen Paul E. Finke Bryan Oates Malcolm MacCoss Sander G. Mills Lorraine Malkowitz Sandra L. Gould Julie A. DeMartino Martin S. Springer Daria Hazuda Michael Miller Joseph Kessler Renee Danzeisen Gwen Carver Anthony Carella Karen Holmes Janet Lineberger William A. Schleif Emilio A. Emini 《Bioorganic & medicinal chemistry letters》2001,11(24):3099-3102
A series of hydantoin derivatives has been discovered as highly potent nonpeptide antagonists for the human CCR5 receptor. The synthesis, SAR, and biological profiles of this class of antagonists are described. 相似文献
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Shen DM Shu M Willoughby CA Shah S Lynch CL Hale JJ Mills SG Chapman KT Malkowitz L Springer MS Gould SL DeMartino JA Siciliano SJ Lyons K Pivnichny JV Kwei GY Carella A Carver G Holmes K Schleif WA Danzeisen R Hazuda D Kessler J Lineberger J Miller MD Emini EA 《Bioorganic & medicinal chemistry letters》2004,14(4):941-945
Modifications of the alkyl acetic acid portion and the phenyl on pyrrolidine in our lead pyrazole compound 1 afforded the isopropyl compound 9. This compound is a potent CCR5 antagonist showing good in vitro antiviral activity against HIV-1, an excellent selectivity profile, and good oral bioavailability in three animal species. During this investigation, a new method for the preparation of alpha-(pyrrolidin-1-yl)-alpha,alpha-dialkyl acetic acid from a pyrrolidine and alpha-bromo-alpha,alpha-dialkyl acetic acid using silver triflate was discovered. This allowed us to prepare compounds such as 24 and 25 for the first time. A novel Pd-mediated N-dealkylation of alpha-(pyrrolidin-1-yl)acetic acid was also uncovered. 相似文献
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Shen DM Shu M Mills SG Chapman KT Malkowitz L Springer MS Gould SL DeMartino JA Siciliano SJ Kwei GY Carella A Carver G Holmes K Schleif WA Danzeisen R Hazuda D Kessler J Lineberger J Miller MD Emini EA 《Bioorganic & medicinal chemistry letters》2004,14(4):935-939
Replacement of the flexible connecting chains between the piperidine moiety and an aromatic group in previous CCR5 antagonists with heterocycles, such as pyrazole and isoxazole, provided potent CCR5 antagonists with excellent anti-HIV-1 activity in vitro. SAR studies revealed optimal placement of an unsubstituted nitrogen atom in the heterocycle to be meta to the bond connected to the 4-position of piperidine. Truncation of a benzyl group to a phenyl group afforded compounds with dramatically improved oral bioavailability, albeit with reduced activity. 相似文献